There are 4 total sizes. The large ones are pretty large, but there are only a few of them. There are more of the two smallest sizes, which is a bit of a bummer since the largest stars are the brightest.
the smallest ones should be about 1-1.5cm (I'm estimating because they're all up on my ceiling now and it's sort of... high up) and the largest one is 3.5 inches (this one I measured) :) hope it helps? It comes in extra small, small, medium, large :)
I'm sorry that I don't have dimensions for you. I can tell you that this particular set had more large stars than others I looked at. I can also let you know from previous experience that even the little stars show up nicely on the ceiling. But, again, sorry I don't have actual dimensions.
I'm sorry that I don't have actual dimensions. I wanted that information, too; but, I can let you know that when I was pricing different sets this one had the most amount of large stars. I was happy with it when I received it, and my grandson and his father seemed happy with it when I gave it to them. I can also tell you from experience that although I wanted larger stars, too, a previous set I had came with tiny stars and yet they were also quite visible. Sorry I don't have more facts.