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Color: Black|Size: Two wristbands 1 large and 1 small|Change
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TOP 50 REVIEWERon January 11, 2014
Update 12/8/15 - Fitbit just added a new firmware update for the sleep timer feature. Once updated it's no longer necessary to tap the Fitbit before going to sleep or when waking it. It will now recognize when you're inactive and have gone to sleep. It also has some new goal setting software in the app relating to sleep to make it easier to focus on getting more (or less) sleep. The graphic interface is pretty nice. I'm looking forward to using this since I've become something of a night owl and could really stand to get on a better schedule. One more thing to like about my Fitbit.
The update took about 5 minutes using my iPad and plugging my Fitbit into its charger while it updated. The whole thing was simple. A red arrow on the dashboard, in the sync area alerted me to the upgrade. I really like this new feature.

I bought 3 of these fitbit flex devices, one for myself, my husband and my sister. Before purchasing I researched several wristband devices such as the Jawbone UP, the Nike Fuel and and the Polar Loop. I also looked at the fitbit force which is a newer version of this band. The lack of water resistance on the force was a deal breaker for me. I wanted to be able to wear this band 24/7 and to be able to wear it in the shower or when swimming. That was part of what made it attractive to me. Also, after reading reviews about the clasp problems on the force and how many people lost them, I wanted no part of that. They are also quite a bit bigger and look clunckier. The wristband on the UP looked like it would catch on everything and had no display at all. The Polar had lots of quality problems. I wasn't crazy about the looks of the Nike. The display is nice and I can see how people would like them, but not my style. The fitbit flex, to my tastes, had the coolest look. I also know a couple of people who own the fitbit flex and they were very enthusiastic about them so that influenced me as well.

So here is what I like about the flex: I like the way it looks on my wrist. All of us got the slate color. You can also order bands in a few different colors, both here and on the Fitbit site. It is lightweight and even though I don't often wear a watch I don't notice this on my wrist at all. The clasp was VERY difficult to secure the first couple of times until the rubber softened up a bit and until I got the hang of it. I secured it off of my wrist a couple times when it was new. Making sure the band and clasps are lined up correctly and then placing one finger directly below the clasp and my thumb directly above and squeezing hard was the way to do it.

I like that it's water resistant and that I can wear it swimming or in the shower. It is safe down to 10 meters or around 30 feet. I like that the wristband is made of TPU rubber, which according to Wikipedia is a type of rubber used in automotive instrument panels, caster wheels, power tools, sporting goods, medical devices, drive belts, footwear, inflatable rafts, and a variety of extruded film, sheet and profile applications. I think it should hold up for a very long time. I like that the display on the band gives me a rough idea by tapping on it of my progress throughout the day. I can also check my progress on my iPhone 4S and see number of steps so far, calories burned, how many hours of sleep I got last night and how often I woke up or was restless. So far it seems very accurate. I can also track the foods I've eaten and the calories, my weight goals and weight lost, check on the weekly number of steps friend's with Fitbits have taken and compare them with my own.

I like that I can wear it 24/7 and only have to take it off to charge it once every 7 days. It takes about 3 hours to charge with a USB thingie that comes with it. I use a wall adapter to charge it but could also use a USB port on my desktop or laptop computer. I've lost too many pedometers in the past by dropping them out of my pockets or forgetting about them and sending them through the washing machine, so the wristband seems like a much better option for me. I also like that I can connect wirelessly with my smartphone and with the little dongle included that goes into my desktop or laptop, can connect with those wirelessly as well. Software downloads for all of these are free. I'm also able to connect on my first gen Kindle HD 8.9 although I can't see where it's shown as a supported device so far. But it works with the Android fitbit software in the app store.

The step measurements seem reasonably accurate. Waving my hand slowly won't register as a step. Waving wildly will. Driving in the car won't register but reaching around quickly in the car sometimes will. Typing on the computer or Kindle won't register. I've heard that swimming doesn't register either but you can input the time and activity on your phone or tablet. When I first got the flex I started the iPhone app and watched my steps register on my screen as I walked around the house. That, and watching my steps on the treadmill have shown it to be pretty accurate for me, although not perfect. I think that all pedometers have some inaccuracies. What I'm looking for is a comparative trend where I can tell how much exercise I'm getting. The accuracy is good enough for me.

So I wake up in the morning, tap the wristband quickly a few times to tell it I'm awake. Then if I tap it twice I see one tiny blinking light, telling me I'm working on my first 2,000 steps. Later, when I've hit that mark and tap to check again, I'll see one solid light and the second one blinking. There are 5 lights total and each represents 2,000 steps (or 20% of my goal. I could set it up differently on my computer, using a different number of steps as my daily goal if I wanted to.) So I can see my approximate progress any time during the day. When I hit my goal of 10,000 steps the band vibrates and all the lights flash. That means you done good!

I can set up to 8 silent vibrating alarms on this fltbit. I have one to wake me up on weekdays (you can specify which days) and one at 8:00 each night to remind me stop eating for the day. The vibration gets my attention and is effective at waking me up. I set the alarms on my computer or phone.

At night when I'm in bed and ready to go to sleep I tap the wristband rapidly a few times, it vibrates briefly, and goes into the sleep mode until I wake it again in the morning.

So am I happy that I purchased the Fitbits for myself and my family members? Yes I am. It motivates me to walk or run more. I can connect to other friends and family with Fitbits to see everyone's weekly step progress but what really motivates me is just competing against myself. I'll find myself parking in the back of the parking lots at stores to log those extra steps or walking around the store longer because it's a good way to add even more. When I haven't reached my goal at night, I'll sometimes walk around the house several times just to hit a number. Now that can't be all bad, can it?

Update 1/12/14 - I'll keep updating this review with comments and observations as I use this device. I noticed that walking at a rapid pace is counted as "active minutes". Someone on a message board suggested adding a touch of lotion to the clasp if you're having trouble getting it to clasp when it's new.

Update 1/16/14 - A full charge is lasting just a bit over 7 days. It takes about 3 hours to recharge it fully.

Update 1/21/14 - Some people have complained about this band coming undone and losing it. I haven't had any problems with it at all, even when pulling tight coat and shirt sleeves over it, brushing my arm against things or the dog pulling on it once or twice. (I'm sure the dog could have pulled it off if I didn't stop him.) The other day I had the dog's leash wrapped around the wrist with the Fitbit and even with the dog pulling against the leash the fitbit stayed on. We walked this way a couple of miles before I noticed it and unwrapped the leash from my wrist. But even with all that agitation my fitbit stayed put. It has stayed on through enough that I'm not very concerned about losing it. I've only taken it off to charge it. I have the band snug enough that I can only put one finger beneath the band but I can move it a couple of inches back and forth on my wrist.

Update 7/3/14 - A new update that works with iPhones that use the Fitbit app was released a few days ago. I've used it with my iPhone 4S and really like the new upgrade. It adds a whole new dimension to my Fitbit app. With the upgrade, I just click on the exercise icon on the dashboard which takes me to a new screen showing the days of the week that I've exercised. (Meaning a walk, run or hike, something in addition to the regular walking in my daily activities.) This screen shows exercise frequency by day of the week, it puts a check on the days that you do some planned exercise. If I click the little stopwatch in the upper right-hand corner, it takes me to a screen where I can click Walk, Run, or Hike. I go back and can then click Cues which takes me to another screen where I can select whether or not I want to hear spoken cues. I can also tell it which cues I want including: Distance, Time, Average Pace, Split Pace, and Calories Burned. Then I go back again an can select the frequency of the cues from every .5 miles to every 5 miles. Or, I can make the cues time based ranging from every 2 minutes, 3, 4, 5, 10, 15, 20, 25, or 30 minutes. I can also select the volume of the cues. (Medium was perfect for me.) Then, back again to select a playlist from my iPhone's loaded tunes. Last, I allowed location services for Fitbit in my phone settings and I was ready to go. Now I see a big red circle with a Start arrow on the screen over a GPS map showing my location. I pop in my earphones, click Start and my music starts playing.

As I walk, I can see a screen showing how far I've walked, rate per mile, time elapsed. Every half mile a voice interrupts my music telling me how far I've gone and all the other things I've specified in Cues that I wanted to know. Then it goes back to playing my music until it's time for my next designated Cue. How cool is that? It works seamlessly. At the end of my walk I tell it I'm finished (or I could also pause it if I stop to talk to a neighbor or something). When I'm finished (or even during the walk or run) I can see a little red line showing my route on the map. The steps from my walk are added to my steps count, just as they always are. I love these new features. They add a lot to the Fitbit experience.

For those of you who track calories and foods eaten in the Fitbit app, the update now includes a bar code scanner. So far, the things I've scanned have been in their database. If you don't see the bar code symbol in the upper right-hand corner of the Log Food screen, log out of the Fitbit app and then log back in and it should be there.

Update 11/28/14 - If something happened to ithis Fitbit today, what would I replace it with? Another one just like it. If one of the new Fitbit models was interchangeable with it on a daily basis I might get one of those too, just because I like new technology. But this one would be my main fitness band. I would like having a watch built in, but then it would look kind of silly wearing a conventional watch on the other arm. And I have a lot of nice watches.

Update 12/12/14 - I just noticed today that the Fitbit Flex is the #1 Best Seller on Amazon this holiday season. It does seem like when I see people wearing fitness bracelets, this is the one they're most often wearing. A lot of the competitors have lowered prices significantly on their devices which is probably the best indicator of all. It's nice to know that I'm not the only Fitbit fan after wearing it for nearly a year. :)

Update 12/26/14 - My Fitbit looks all new for the holidays. This replacement bracelet took over 20 days to arrive but for about $2 it was worth the wait.1pc Small S Black with White Dots Spots Replacement Band With Clasp for Fitbit FLEX Only /No tracker/ Wireless Activity Bracelet Sport Wristband Fit Bit Flex Bracelet Sport Arm Band Armband A couple people have asked me how the bands hold up over time. I have to tell them that I don't know since I'm wearing different colored ones almost every day. They don't have much of a chance to show wear.
After almost a year of wearing these 24/7, none of us have had one come off accidentally. Even the cheap knock-off bands seem sturdy and reliable like the original. And I'm not a very careful person about pulling tight sleeves over it or draping grocery bag handles over my arm.
I have the steps across our back patio counted out by counting them myself. It is 60 steps back and forth once. (Yeah, I know, way too anal.) Oftentimes when I haven't hit my 10,000 steps for the day, I'll go out and walk back and forth with my iPad on the patio table to check my progress. I know from doing this that the Fitbit step count is dead-on accurate for counting steps when walking. Dancing will add steps which I think is fair since it's at least as good as walking for exercise.

Update 1/30/15 - I can't believe I've had my Fitbit Flex for over a year already. I'm still wearing it 24/7 as a great motivator to keep moving. I've had several people email me with questions about the way it counts steps so I thought I'd share this with you. I tested another fitness band recently, wearing it on the same arm as the Fitbit. The other band recorded a lot more steps than the Fitbit. I've "manually" counted steps while walking around different areas around my house and compared them to the Fitbit and found them to be exactly the same. But I never did it for more than about 100 steps. Now I was curious because the readings on the two bands were so different. So I went for a walk and counted out 1,000 steps as I took them, counting in my head. (Mumbling under my breath, actually.) Before I started, I noted the starting number of steps on my iPhone for both bands using the apps for each. At the end, I checked the number of steps for both bands. The Fitbit recorded 1004 steps. The other band recorded 1,217. Only 4 extra steps on the Fitbit is pretty impressive and is close enough for me. I'm contacting the manufacturer of the other band to see why it's so far off.

Several people didn't realize that you can adjust the stride for the Fitbit. Just log into the dashboard in your Fitbit app, click on the little gear thingy in the upper right hand corner and select "Settings". There's a field there for Stride Length and Running Stride Length. You can manually enter your personal stride length. If you leave these blank, the app will estimate the values based on your height and whether you are a man or woman. Click the "Update Profile" button to save your changes. Remember to sync to update your tracker with the new stride measurements. I didn't even realize I could do this until several months after I had my Fitbit. I guess it must have estimated correctly in my case because when I put it in manually I didn't notice a difference.

Update 4/30/15 - Fitbit has an update that now allows you to track multiple Fitbit devices on your Fitbit app. I haven't tried this, but from what I understand this will allow you to go back and forth between other models and once registered it will recognize them automatically. It's tempting to try the Fitbit Charge or the Surge that can measure heart rate or pulse or have caller ID. They're bulkier than I would like to wear on an all-the-time basis, but would be nice for workouts. And new technology is always fun. The Flex is still my first love and I like the switchable bands, but I'll look at the new models now that it isn't an either/or decision. Here are their instructions for adding another Fitbit:

Update your Fitbit app (if you haven’t already)
‘Set Up a New Fitbit Device’ from the Account tab in the Fitbit mobile app or Fitbit Connect
Finish the setup instructions, and start swapping – we’ll take care of the rest!

Update 5/7/15 - Has everyone seen the new Fitbit commercial? I usually fast forward through TV commercials on the DVR, but this one I recorded and kept until I could find it on youtube: This makes me smile every time I watch it.

Update 1/24/16 - When I purchased my Flex a little over 2 years ago it was advertised as being "Water resistant to 10 meters or 33 feet" which is 1 ATM. Their website now states: "Flex has been tested up to 1 ATM meaning it is sweat, rain and splash proof. However, the device is not swim proof. We also recommend taking Flex off before showering because, as with any wearable device, it’s best for your skin if the band stays dry and clean." The definition of 1 ATM, as I understand it is that it indicates that under static (nonmoving) conditions at 10 meters below the surface of the water the pressure of the water will not breach the seals on the device. But I can't take it into the shower? Perhaps even more confusing is the Fitbit Surge is rated at 5 ATM (50 meters) and has the same warning about not being swim proof and not to be worn in the shower. Are they just trying to ensure that users don't abuse the tracker?
That said, I always shower with mine, I never dry it off afterward except the top when I'm drying my arms. I don't swim often but when I do, I leave it on. If I were going to spend a lot of time swimming on a regular basis I might take it off since it doesn't track swimming anyway. But for splashing around in a pool occasionally, I don't worry about it.
My skin is somewhat sensitive to watch bands and I'm allergic to some metals and other materials. I couldn't be much LESS careful about the Fitbit and have never had a problem with the band and my skin. The underside is often damp from getting wet in the shower even half an hour later and it hasn't bothered my wrist. Being able to wear this 24/7 was a major selling point for me and it has worked just fine since January 2014.
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Several asked my opinion of the Flex after I had compared UP to ONE last fall. I'm more pleased with Flex than expected. This review will be specifically for those comparing the Jawbone UP to the Fitbit Flex. For those interested in my review of the One and Jawbone UP it is located here: UP by Jawbone - Large Wristband - Retail Packaging - Onyx:

UPDATE: I uploaded several head-to-head app screenshots.

UPDATE: I've found that I am storing quite a bit of water in the Flex band pouch where the module goes. Even though they say it's shower safe, I'm pretty sure some funky stuff is going to be growing in there in a matter of time... But the band is replaceable!


My journey with personal monitoring devices/pedometers started a LONG time ago: Before Fitbit even existed, with a device called the SportBrain. It was a traditional belt clip style so old that it plugged into a base that used a dial in phone modem to upload the usage data to a server. It was old. But my interest in devices that can help monitor and tell me about my activity started then, and we seem to be now in a golden age of personal data monitoring devices. Fitbit Flex, Jawbone UP, all of the Fitbit clip devices and so many more...

Hardware itself

The biggest drawbacks I found on the Jawbone UP were that it had no visual feedback about your daily achievement toward your goal and the fact that it had no visual battery indicator. It wasn't a problem for me personally, but for those who are hardcore driven on a daily basis to compare and achieve this could be a drawback for you. The next drawback about the Jawbone UP is that it does not wirelessly sync. You have to plug it into the headset jack of your phone to sync. If you are someone who wants data and feedback all day long, this would be a drawback.

The Fitbit Flex does have visual feedback in the form of small white lights: They blink as you're charging, they have a special blink if you put it into sleep mode and provide 95% more feedback than Jawbone up. Jawbone UP does have status lights in it and they are used, but they could do a lot more with the lights they already have if they chose to.

If you can throw a snap bracelet on, you can easily put on the UP. I did find myself fumbling a bit with the clip mechanism of the Flex like I do when I have to button my own shirt cuffs. After it was clipped though, it feels secure and I am not one to put on and remove devices like this. I want to set it and forget it.

Fit & Feel

The Fitbit Flex feels very comfortable on the wrist. The pictures don't do it justice. For me personally this is the one defining factor that really makes the Flex shine for me compared to the Jawbone UP. It feels super light weight, doesn't grab, and doesn't look nearly as big/thick as the pictures make it look.

The UP uses tension to stay on, while the Flex uses a clasp. The UP may have a better sense of solid attachment that wouldn't come off no matter how hard you fling your arm, but the inverse of that is the Flex: It doesn't have to monkey-grip your arm to be there and stay. You can have it fit a bit more loosely than UP and be comfortable.

When typing on at a keyboard, I prefer the feel of the Flex. The rubber is flat and thin so it adds very little against the edge of a keyboard. The UP doesn't have the big square bump on the top, but it does have a bracelet shape/size all the way around, so it can prove a bit more of an annoyance up against a keyboard.

The Flex does have replaceable bracelets and colors, which means the device is more convertible and flexible going forward. That being said, it is less visually appealing to me compared to the UP. The UP can be a part of jewelry and most people would never notice. The Flex does have a strange-ish future nerd look to it. I don't mind that, but some may.

I wear both in the shower with no issues. I've done a lot of swimming pool roughhousing with the UP with no issues, but haven't tried with the FLEX. A commenter tells me that it is swimming approved, though the data provided might not be that useful.

Battery Life & Charging

Both the Flex and the UP charge in very similar almost identical USB adapters. They're meant to be charged on a computer and in my experience shouldn't be charged off of a phone USB wall charger. They both charged in similar amounts of time, and the Flex did last about 4 days on a charge. The UP can last as much as 10 days on a new battery, but I found that it has declined some since November. On this case, I say that both do about what they suggest. The UP fits snugly in the charger, while the Flex doesn't feel nearly as secure in its charger but I haven't had any issues with it falling out.


The Jawbone UP sync's via the headphone jack of the phone. It doesn't do Bluetooth, can't be plugged into a PC, so you're pretty much set on a smart phone or table to sync it. It's simple, doesn't consume battery to sync wirelessly, and works reliably. You have to watch because not all phones are supported.

The Flex syncs wirelessly with Bluetooth 4.0 via the smartphone or via an adapter to a computer. For those without a smart phone or a locked down phone that work doesn't allow you to install apps, this could be a deal maker for you. It's not a constant sync but initiates as soon as you open the app on the smartphone. I haven't noticed any significant battery life loss. Not all phones are supported with Bluetooth 4.0-- most phones on the market don't yet have Bluetooth 4.0. You'll want to check Fitbit's website to see if your phone is supported. On the upside, the Flex does come with a Bluetooth adapter you can plug into a PC or Mac to sync wirelessly via the computer. It really adds extra work and decreases the usefulness of wireless sync, but it's do-able.


The software, to me, is the major differentiating factor between the two devices. The hardware looks entirely different, and there are some small differences in what the hardware can do, but the delivery through the app is what makes them clearly meant for different targets.

The Jawbone UP software is beautiful. After you've sync'd enough it starts giving you feedback and encouragement through statistics. It will tell you "you were in the top 15% of UPpers this week" or "getting 8 hours of sleep per night it shown to improve...." if your sleep is coming up short. It does have the option to add in food consumption, performs a variety of tasks such as calibrating it's readings with actual distance walked, and has a really interesting "lifeline" feature that trends your activity & sleep over a period of hours, days, weeks and you can create a report on the fly comparing, for example, sleeping and calorie intake, to see if you consume more calories on days that you didn't have adequate sleep. It shows trends on daily/weekly and true to the marketing is a more "holistic" view of you and your life/activity. I guess we have reached my thesis for the comparison: Jawbone UP is about the holistic view of your life, while the Fitbit Flex is more finely focused on activity, seeing feedback for that activity in a quick frequent way and focusing on providing you that core data quickly and simply.

The Fitbit software is the same software in use for all current Fibit devices. As soon as you launch it, a sync begins and your latest data will be presented. While the UP presents more current data on the "HOME" page, Fitbit has other tabs where you can explore the data they present. UPDATE: I discovered that the Fitbit software does do single activity trending if you turn the phone sideways: Hours/days/weeks, etc. It doesn't compare it to another statistic, but better than nothing.

Both devices sync your data to a website. The Flex presents a more insightful view of your data on the website, while UP presents an equal amount of that data on the mobile app. Both support third party apps if you are really intense about a specific subject ( like food/calories with extensive catalogues, MyFitnessPal, etc.)

A few features that the Flex has that the UP does not:

-Lighted feedback on the band
-more flexible fit, colors that can be changed after purchase
-Thinner band around places you may bump against desks, etc.
-wireless syncing (Jawbone needs to get on this train)
-quick access in the app to 'water consumed'

Fitbit Flex: Less expensive, simple quick device for activity & sleep tracking and wireless syncing from a company that is widely known for pedometers.

A few features that UP has that Flex does not:

-insight engine to look at your data and provide you feedback
-longer maximum battery life
-inactivity alarm. Fitbit could easily issue this in an update. I love this feature on the UP
-bar code scanner in the food app to scan premade food for nutrition contents
-power nap which will auto wake you between 25-45 minutes by modeling after your normal short sleep cycle

Jawbone UP: Technology that could pass for fashion. A fantastic app with a holistic view on your life, sleep and wellness.

Both devices are good devices and had no fatal flaws. Both devices offer communities and ability to add friends to provide encouragement and interaction. If I had to give an elevator speech about the difference between the two:

1. A few tech differences: Flex has wireless sync and quick feedback throughout the day. Flex is thick on top, and thin around. UP is more consistent without a clasp.

2. UP has a very useful insight engine and is more of a "holistic" view. Less rewarding for someone who wants instant feedback. It's all about your time horizon: If you want to look at days and weeks of data, receive valuable feedback about your activity and sleep patterns and wellness the UP will probably please you most. If you are someone who wants hourly motivation and ability to sync frequently then the Flex is probably the right device for you.

I hope this comparison has been helpful. If you have any specific questions I will be happy to answer or investigate & answer. My personal lean is toward the UP simply because I am using it to observe my sleep and activity from a bigger picture view. Sometimes I may go a day or few before I sync. If I were in a mode for physical fitness or weight loss, I may probably prefer the Flex. It all depends on your objective. There really isn't a fight between these devices-- they're both good and are focused towards different crowds.

UPDATE: I found an interesting quirk with Flex: I was shopping at a store today and the shopping cart had a wheel that was a little bumpy. During my shopping I felt a vibration from Flex and thought maybe I had made a part of my daily goal. Then: BZZ, BZZ, BZZ! Turns out that the bumping of the cart in a rhythmic way confused the Flex into thinking I tapped it. It kept going in and out of sleep mode. Whoops. I can't wait until I see today's data....
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on April 16, 2013
The Flex is fairly good - IF you understand its limitations. And it has a lot of them. This is a 1.0 version, the first wrist-based tracker Fitbit has produced. There are good reasons why there are so many negative reviews of the Flex. I strongly suggest that you wait for the technology to be refined by Fitbit (and others) before spending $100 or more on this.

I also suggest that you tune out the 5-star "this is AWESOME!" reviewers. I've had the Flex for 6 months now (acquired at CES 2013, long before retail availability) and initially I too was impressed by the technology. However, with long-term use, I think its inaccuracies make it nothing more than a pedometer with sleep analysis added in (and the usefulness of the latter is dubious as well). The IDEA of it all is excellent: to track your activities and see your progress over time via the great software that Fitbit has developed. However, all of this is predicated on the device accurately tracking your movements. If it fails in that aspect - and unfortunately it does, to a moderate degree - then all of the data and impressive charts and graphs are rather useless. The "awesome!" reviewers don't realize this (yet) and just assume what they're seeing is real; it isn't.

The underlying technological problem, as I see it, is in the placement of the tracker. Up until now, Fitbit trackers were to be placed on the torso. Now, it must be placed on the wrist (yes, the tracker itself can be taken out of the wristband and put into your pocket but all of Fitbit's calibrations and algorithms are designed for that wrist placement and you are making the problem worse by not having it on your wrist). So, if your wrist movement is ANYTHING other than the usual movement of either running or walking, your step count/mileage is going to be off - often way, way off.

Fitbit markets the Flex as an "activity monitor", implying that it is capable of keeping stats on your physical activities. Well, because of the wrist location issue and the basic design structure of using two stride lengths for all calculations (your walking and running stride lengths), pretty much any activity that is NOT walking or running cannot be accurately monitored: the accelerometer senses whether you are walking or running and multiplies the appropriate stride length by the number of steps sensed (and arrives at a mileage distance). Any activity outside of that limited ability of the Flex, your stats are innacurate. This includes stair-climbing, hiking, tennis, golf, biking, working out, and pretty much every other "activity" that is not walking or running. The Flex is not really an "activity monitor"; it's an expensive pedometer (albeit one with "sleep analysis", which is actually only a record of how much wrist movement you had during the night: i.e., 2 hours of no movement = deep sleep, an hour of sporadic movement = restless sleep).

There are, however, aspects of the Flex that are quite good: it does accurately keep track of your walking and running, it does keep track of your sleeping patterns, and it also wakes you with a silent vibration on your wrist at the time you set to get up in the morning. And once out of bed and into the shower, there's no need to take the Flex off: it's almost completely waterproof (pressurized water being the exception). But the best, perhaps life-enhancing aspect of the Flex is its ability to keep you focused on your exercise goals (which is the main reason why, overall, I like the device and its software - to a point): if you DO consider it only a pedometer with cool software, which is what I consider it to be, you will not be disappointed (though the price may not seem worth it to others).

First, there's the 'onboard' function to keep you aware of your progress towards your daily goals (total distance traveled, number of steps taken, or calories burned): each light on the row of 5 small LED lights on the band represents 20% of your goal and a quick glance and a tap on the band will tell you how you're doing. Secondly, for the actual stats of your progress (or reviewing your daily, weekly or longer stats), you can view them in real time on your phone via the Fitbit App for iPhone and Android, or on your tablet or PC/Mac with the Fitbit 'Dashboard'. This is where you set your daily and longer-term goals, view not only your stats but see them represented in charts and graphs, and log other information such as weight, weight changes, and food consumed. You can go further, but personally I would feel a bit silly setting goals where I would receive 'badges' for reaching them. But that's just me. Overall though, the software is very good and keeps you aware - along with the band's LEDs - of whether or not you are staying on track of exercise goals. But, again, just keep in mind that the wrist placement of the device gives the Flex an inherent flaw as to the accuracy of all this data - UNLESS you are using it only to monitor and analyze walking and running stats, as I do.

If you're like me and the term "highly-motivated" (or "disciplined") and your name rarely appear in the same sentence, the Flex is a great help in that regard: it makes you keenly aware of whether you're succeeding or failing in your exercise regimen, which I find to be a great help in discipline and motivation. The Flex is a good motivator because you do not want to have today's exercise stats look inferior to yesterday's - or this week's less than last week's - or this month's less than last month's: you can graphically SEE all this on a color graph, your success or failure staring you right in the face. And who wants to stare at his or her failure or laziness? We want to see improvement, to see success. And, for me, this is why the Flex is a valuable tool: an ever-present motivator. I personally use it for running and I find that I really push myself to prevent the present week's stats (total mileage, etc.) from failing to outdo last week's. Seeing the charts and color graphs of several months of steady progress, there's a real feeling of accomplishment and a strong motivation to continue. It is this visual presentation of your exercise efforts that sets the Flex (and other Fitbit models) apart, in my opinion.

Is the Flex a miracle device that will accurately detail your every movement, every calorie burned, throughout your day? No, it's an accelerometer/pedometer based on your stride lengths and your wrist movement; there are many activities where it is impossible for such a device to determine steps, etc. Fitbit's marketing of the device was overblown, calling the Flex an "activity monitor/tracker", implying - to many - that all activities could be measured for steps/mileage/calories, which is not the case. Further, Fitbit should not be marketing it as a calorie monitor because an accelerometer alone (which is what the Flex is) cannot possibly count calories burned with any real accuracy.

So, overall, I would give the Flex 2 stars, based on the way it's marketed to the general public. It does fail to live up to many buyers' expectations (read the many 1- and 2-star raging reviews). The technology required to do what Fitbit infers the Flex can do - tracking and monitoring most physical activities - is probably a few years away. Someday there may be a Flex with integrated GPS, heart-rate monitor and an accurate altimeter: THEN we can expect steps/mileage/calories counts to be done for many more activities. For now, this Flex ("Flex 1.0") is basically a pedometer (with a few other features) and its accuracy is limited to a narrow range of activity. My personal needs happen to fall into that narrow range: I use it only for running and walking exercise and in analyzing, graphically, my fitness history and progress via the Dashboard, and it's a great motivational tool. For my personal needs, I'd probably have to give it 3 stars (but this would be misleading to the average Amazon buyer). Unless your personal needs are as narrow as mine, I would hold off on buying the Flex until improvements are made. You can duplicate this model's limited abilities with a decent pedometer and freeware/shareware to manually input and analyze the stats.


There have been so many good questions about aspects of the Flex that I didn't cover originally that it's probably best that I expand the review:

LOCATION OF TRACKER: Early questions asked about whether or not you can wear the tracker outside of the band or with the band around your ankle, etc. (earlier Fitbits could be worn anywhere on the torso). It is only accurate on your wrist (or, rather, it is most accurate on your wrist, its overall accuracy pretty questionable).

ACCURACY OVERALL: For usual activities like walking and running, if you see inaccuracies in mileage or number of steps, probably your stride measurements are not like the average person for your height (which is what Fitbit uses for default strides, your height entered when you set up your account). In your account settings, you can change 'Stride Length' and 'Running Stride Length' in order to calibrate the accuracy. Ignore the reviewer who states that you can't calibrate the Flex: you can; all the tracker is doing is counting steps (and multiplying those steps for mileage amounts); since you can adjust your stride lengths, you can calibrate the Flex to your exact needs. The device has a walking step (stride) and a running step and counts them (and converts your steps to mileage). The only way to have accurate mileage is for the Flex to KNOW your two stride distances and to have the wrist tracker sense whether you're walking or running; if you mess with those dynamics (irregular steps, irregular wrist movement), you mess with accuracy, simple as that.

There is an additional tweak to minimize wrist movement inaccuracies: you CAN go into your dashboard settings and change the location of the wristband from 'dominate hand' to 'non-dominate', but I've found that this to be of little use: the Flex is only reliable when walking and running AND having normal wrist activity while doing so. Instances where one wrist is more active than the other are not likely to be in walking and running activities.

WATERPROOF: It is not entirely waterproof. You can wear it in the shower or along the surface of a pool. However, it's not rated to withstand water at depth - water where there's pressure.

STAIRS: Unlike its predecessors like the One, the Flex does not have an altimeter and therefore cannot count stairs climbed. From what I read, Fitbit did away with it because it was inherently inaccurate.

BANDS: The Flex comes with both a small and a large band. The large band goes from about 6 1/4" to 8 1/4" and the small, 5 1/2" to almost 7" and both are fully adjustable between those lengths. Putting on the band is difficult the first week or so - the rubber is a bit stiff - but then it becomes looser and easier to put on.

TREADMILLS: Your 'Running Stride Length' on a treadmill may be shorter than on the road (no forward momentum). See above about tweaking stride lengths.

HEART RATE: No, there is no heart rate monitor.

CALORIE COUNTS: The Flex really should NOT be marketed as a calorie-burning monitor. No device without a heart-rate monitor can accurately determine calorie burning. But when using the Flex to simply analyze a run or a long walk, it can 'ballpark' calories burned fairly well; expecting it to tell you how many calories you burned in the past 24 hours - not so much.

SUBSCRIPTION: For your normal account there is no additional charge for anything but for a 'Premium Account', which gives additional analysis and tips (such as a 'Fitbit Trainer' 12-week plan, more data analysis, a 'peer ranking', etc.), it is $49.95 per year. The Premium doesn't really seem worth it, to me, but then again it's only $4 a month or so for someone who wants to get more from the Flex.

SLEEP MODE: There are two options for sleep mode. One is automatic and does not require you to "tell" the Flex that you are going to sleep, like the Up and and other competing models; however, you do need to log your sleep hours on your dashboard; at the next sync your sleep data will be visible. Alternatively you can fast tap the band when going to bed and do the same when you wake up. Personally, I prefer the dashboard method as I would probably forget quite often to tap the band. The Flex determines amounts of restful vs. wakeful/restless sleep simply by wrist movement (i.e., no movement for 2 hours = restful sleep). The novelty of being able to analyze your sleep patterns soon wears off, at least in my case; the usefulness of the data seems questionable.

ANDROID COMPATIBILITY: You need Bluetooth 4 for real time syncing.

CHARGING: It takes about 2 hours to fully charge using the dedicated USB cord. The battery lasts about a week.

OVERALL OPINION: I did use the thing for months: it kept me motivated by being able to compare walking and running stats over time via the software interface. Otherwise, it was no better than a decent pedometer (and triple the cost). It fell apart after 3 months, like it seems to do quite commonly. Remember that this is the 1.0 version of the Flex, so enhanced capabilities - and better quality overall - may not be too far away. Perhaps the Flex 2.0 will be worth the list price if improvements are made but this 1.0 version is really not be worth it for most people. Read the many 1- and 2-star reviews as evidence of this. And, again, do not trust the mountain of 5-star reviews: if you look at them, 90% are 5 words or less ('Love my Fitbit!'), written by people who have no idea as to whether all the shiny color graphs and step counts are accurate or not. They are not, for reasons explained above.
264264 comments|7,507 people found this helpful. Was this review helpful to you?YesNoReport abuse
on January 5, 2016
With such a wide variety of fitness wristbands out in the market right now, it was becoming really difficult to choose one that would fit my necessities. I researched for a long time to able to come up with my top picks. I was able to find a great site that really helped me compare all the models available with their different features. I was able to find the right one for me and the great thing is that when I finally decided which one was the best fit, I could just click on the chosen one and it will immediately direct me to an amazon store to purchase it.
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on April 6, 2016
I have used several fitness trackers including the Garmin and this one is the best. It keeps me motivated every day to make sure I get enough exercise. However, exercise alone was not helping me lose the weight I wanted, so I also went on a no carb diet, and use Atrafex for 2 months. Atrafex Thermogenic Fat Burner & Appetite Suppressant The end result? 4 pounds lost and in nearly the best shape of my life. Highly recommend it.
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on May 3, 2013
My wife and I purchased our Flex bands early at Best Buy like so many others have already done. This is my first Fitbit product and activity tracker, so please keep that in mind. First off, the product's presentation is stellar and will no doubt be an attractive offer to people checking it out in the store. It comes with two sets of bands (large and small), a USB charging dongle, a USB syncing nub, and the activity tracker itself. One knock I have is the lack of a physical manual that comes with the product. There is literally one piece of tiny paper that just has the setup URL. It would have been nice to have at least a 5-6 page quick guide to how this thing works. Setup is a breeze, just go to the URL listed on the paper, download the software, and sync your tracker with the USB syncing device. It asks you to "double tap" the device to sync, I felt like a neanderthal trying to find a button to press. All you need to do is tap the top with your index finger like you would a mouse button.

Getting the tracker in and out of the different bands is easy and it becomes obvious when you put it in the wrong way. Actually putting the band on your wrist is a different story. It's comfortable when you have it on, but it's difficult to push the clasp together to hold it on. It becomes especially difficult with the smaller band because you have less room to work with. See, you want to have the band on snugly so it doesn't move around, but in order to do that you can't have a finger inside of the loop to help push the two ends together. It doesn't feel like it wants to come off when you do have it on though. Also, I spend a lot of time at my keyboard and it's very comfortable to type with it on. (this surprised me)

My wife and I both have Galaxy S3s and the syncing is pretty seamless. It appears that the syncing frequency between devices is at 15 minute intervals. It takes a minute to manually sync devices, but I don't feel like that's necessary unless you're in desperate need of motivation/feedback. My wife and I went on a walk shortly after we got our Flexes and the devices appears to be accurate, but I haven't really scientifically tested that claim. I read somewhere that these wrist devices sometimes mistake arm movement for steps, but that is not the case here. It's really a bummer that it doesn't have a built in altimeter like the Ultra and I imagine that the 2nd generation Flex will have that built in. As for the activity lights, I thought they would be always on, but instead you have to double tap the device for them to show up. That's not a bad thing, but it's something to note.

The sleep tracker/silent alarm function was a huge selling point for me with this device. I'm a little disappointed that the sleep tracking/alarm isn't as robust as the Jawbone Up's. See, there is no detailed analysis of the quality of your sleep, but instead it only tells you when you slept and when you got up in the night. I realize that sleep tracking (deep sleep vs. light sleep) is pseudoscience, but it would be a nice data point. The alarm will just go off when you set it, so don't expect it to wake you up when you're more "rested" like some phone apps or the UP. (again, more pseudoscience) The silent alarm is really not very silent at all. If you have your wristband up against anything besides your wrist it will vibrate the hell out of it. This isn't a knock against the product, but just be warned this device will wake you right up! The vibrating motor feels just as powerful as any smartphone. Also, there is no automated nap feature like the UP, but the alarm is easy enough to set for your own nap intervals.

EDIT: So it appears that there is a device setting on the Fitbit website that allows you to set the sleep tracking to "Sensitive". This might be more of what I'm looking for as opposed to the binary data of the default setting. (i.e. awake or asleep)

The Fitbit software is pretty standard at this point and should be familiar to most of you. The only difference is the alarm feature is baked right in. It's not the most complete set of features, but it gets the job done and is extensive enough for mobile devices.


- Comfortable (even at a desk!)
- Stylish
- Activity Lights for Progress
- Accurate (this hasn't been fully tested, but will say it is for now)
- Adjustable Size Wristband
- Silent Alarm/Sleep Tracking

- No altimeter
- Sleep tracking isn't as robust as the UP
- Difficult to put on
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on July 2, 2013
I have been a delighted Fitbit user. I purchased my first Fitbit product (the Fitbit One) late March 2013. It was easy to set up and sync. Since then I have recommended this device to a number of people and purchased the product for my husband and Father. I purchased a Fitbit Zip for a friend.

I pre-ordered the Fitbit Flex; it arrived as expected May 17th and once again, I found the set-up user friendly.

I have 2 issues:

The product itself. It died completely with less than 6 weeks of use.

Fitbit support. Response was neither timely nor helpful.

On June 16th my Fitbit Flex began malfunctioning--not fully charging after more than 6 hours plugged into my USB adapter. Then the charge it did should would drain in less than 2 hours. Unfortunately I was not able to contact Amazon within the 30 day window of purchase to initiate a return because I was on a bike tour with limited internet access. I assumed Fitbit would honor its product given the fact the product itself seemed to be at fault. However, I was advised today that because I purchased it from someone else, they would not honor their 365 day warranty.

Once I initiated contact with Fitbit Support on June 27th I waited two days for a response which simply outlined steps I had already taken to try to resuscitate my device. A second response came 2 days after the first, and again the suggested measure was something I had already undertaken. My 3rd response came today advising me they were sorry I was not satisfied. How could any customer be satisfied with a $99 purchase that stopped working at 5 weeks? As of today I own a dead device for which Fitbit offers no replacement.
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The manufacturer commented on the review below
on November 21, 2013
Do not buy this product. FItbit has a great dashboard and is awesome when it works, but they have horrible customer service and will not stand behind the warranty. I purchased mine through Amazon on 9/26/2013 and it stopped working on 11/18/2013. The tracker became unresponsive and stopped syncing and simultaneously the battery started dying within an hour of a full charge. I did not break it, it was not damaged in any way -- it just stopped working.

I contacted Fitbit through the only mode of communication they have - email (case #1023393). I got back an automated message that stated they would contact me within 48 hrs. Later that day I started getting a series of emails requesting troubleshooting, which normally isn't a bad thing. However these emails kept asking me to do the same thing repeatedly and seemingly ignored my responses. I don't know if it is an automated bot of some kind or what. The 'troubleshooting', in my opinion, is designed to irritate users into walking away from the process. They ask questions like "is the computer on", "make sure the computer is not a sleep", "is the battery charged", etc.

After answering all of these ridiculous questions they consider 'troubleshooting' and explaining that the device is broken; I requested a warranty replacement (I even included my invoice from Amazon in the request). The emails stopped! They will not respond, It's been 4 days and they will not even acknowledge the request for replacement.

Do yourself a favor and buy a product from a company that will honor the warranty. I was completely enamored by my Flex, I love the dashboard and it really motivated me to get moving. I however cannot afford to replace a $100 tracker every 50 days and cannot recommend a product that dies after just 50 days. Save yourself the headache and keep searching.
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The manufacturer commented on this review (What's this?)
Hi Clarence,

We are sincerely sorry for the way we handled your case previously. We were able to locate and respond to your case. We're happy to help to resolve this and get you back on track.

Fitbit Support
on March 13, 2015
I have own this device since September 2014; it’s now March 2015. I feel like I have had enough time and experience with this device under my belt to write a proper review.
-This device does not have a clock feature. This would have been nice, I often find myself looking at it trying to find the time only to realize it doesn’t have a clock feature.
-It cannot record other physical actives very well such as biking, cycling, cardio fitness, canoeing/kayaking, stairs, weight training or yoga. It is mainly for walking and hiking. It can detect movement and it can tell when you are being active and for how long but if you are not walking it may or may not record any data.
-It does not have a heart rate monitor feature, lacking this feature might be a deal breaker for some
-This device says it is water proof and I have taken a shower with it on before but a small amount of water will get into the band. Getting it wet won’t cause any damage, but I like to dry it off after getting it wet. So if you get wet with it on plan on taking it off and letting it dry out afterwards.
-The wrist band seems to crack after a few months. The crack continues to spread and grow, until you are worried about the device falling out of the band. The crack happens every time for me right around the area where the device slides in and out, which sits on your wrist when you put the band on. I am always paranoid about losing the device when it is cracked, so to be on the safe side every 3 months or so plan on spending 7-10 bucks on a replacement band. This is a little disappointing! I feel like this problem could be fixed with a better band design or a higher quality material for the band. I guess if not being able to see the light feature was a big deal you could maybe use some duct tape, I haven’t experimented with the duct tape yet, but I have tried super glue which made the plastic band brittle and the crack grew much bigger and at faster rate -so take my advice and avoid superglue as a possible fix option.
-Sometimes when I walk with my arms full of boxes it has a harder time detecting my movement/steps. There are times I have noticed the accuracy of this device may not be 100%. So if dead on accuracy is an issue for you this may not be the device for you
-This device is defiantly better in my opinion that using a walking app on your phone or using a pedometer that you have to clip to your belt or bra strap. You can wear it like a watch and not worry about taking it off or on like a clip on pedometer. I have used clip on pedometers before and left them clipped to my pants and thrown them in the washer accidentally. Which this device at least I know when it is own my wrist. I leave it on most of the time and only take it off to shower and recharge. It is comfortable enough to sleep in.
-The battery life lasts about a week for me, I use an alarm feature 5 days a week. The alarm lightly pulses a vibration on your wrist. I also love the usb charger, makes plugging it in while I am working my computer easy to maintain battery life. It takes about 1.5-2 hours to charge once a week.
-The sleep tracking feature is pretty cool and has helped me improve my sleep quality
-In some ways I love the simplicity of this device. It may not have as many features or bells and whistles, but it does give you a better idea of how much you are walking or a time table for how long you have been inactive. It also allows you to try to gradually increase your physical fitness goals, so this might be a good beginner device for a lot of folks. I have a desk job so being able to see when I have been inactive too long is helpful to me. It lets me visually see, oh I need to get up and move around for a little while or go for a walk on my lunch break; or go for a 10 minute walk every 4 hours.
-The online support & account and features are great! You can set the alarm online, you can track your weight loss progress and create a custom weight loss goals for yourself, which will create a custom walking step guide to help you meet your goals. You can also track your meals, water intake and weight loss. A few of my coworkers go them so we have friendly office competitions with each other.

Everyone is at a different level of fitness and has different fitness goals. If you are a little more hard core with your fitness and want to track your heart rate level throughout your workout this device may not be for you. Overall not bad for the beginners, there are always pros and cons for any device but I feel like this a great device for beginners and much easier to use than a pedometer you have clip to your belt. It has helped me be more consciences of my personal fitness, remember to be more active throughout the day, and helped me set and meet some goals. It has also helped me to improve the quality of my sleep. I would give 5 stars except for this two features I wish they would improve: 1- the wrist band cracking problem 2-adding a clock feature. I know there are 3rd party companies that such as Tory Burch who has started making metal wrist bands for $195. Spending an extra $200 on a band seems excessive I feel like Fitbit should have their own version of alternative band designs for a lower price.
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The manufacturer commented on the review below
on August 27, 2013
I bought this product in May, when it first came out. It worked fine for about three months. I wore it 24/7, recorded my sleep and meals. It suddenly stopped working properly during the last firmware update. The wristband no long vibrates upon reaching a goal or an alarm; it will not sync to my Mac or my iPhone. I only get an error message saying the battery is low, but it is fully charged. Very disappointing.

UPDATE: After my first FitBit Flex failed, I bought another during the summer. That unit has also failed now, just after Christmas. It appears these things last about four months. My idea of a strenuous workout is washing the car, so I cannot see how I wore it out or broke it. I wore it 24/7 to track my sleep, at work, on walks... and wore it in the shower (as it was clearly intended by the manufacturer). Yesterday, it just stopped working, like before. It will not take a charge, sync or anything. What a piece of junk! At $100 a pop, it looks like the yearly cost of using a FitBit is around $300. I cannot wait until Apple makes a wearable product to measure activity, etc. In the meantime, DON'T WASTE YOUR MONEY ON THIS!
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The manufacturer commented on this review (What's this?)
Hello Murray,
We're sorry to hear of the difficulty you've had with your Flex, and would like to help get you back on track. Please open a case with our Support Team at, and we will be happy to provide you with assistance so you can get back to enjoying your tracker 24/7. Please include a link to your Amazon post in the message.

Fitbit Support

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