None of these are as accurate as a good (2-grand) oscilloscope, but this one is more accurate than the other cheap ones. It isn't fragile like the Snark, isn't hard on your insttrument's finish like the D'Addario, and is commendably visible. I give it the highest recommendation. I have perfect pitch, so use it to get the instrument "close" to what is right so as to not frazzle my nerves, and then I use my ears to get it spot on. But this unit gets it as close to accurate as you're likely to find.