Yellow bellied turtles nails.

Question
How long do the nails need to be for it to be a male?

Answer
Hi Devon,

I don't have an exact answer for you, but the nails would be obviously longer than a female's.  Roughly 3/4-1".  They also have longer tails.  They need to be at least 4" or so to sex accurately, though, so if yours is smaller than that you'll have to wait until it grows.  Here's a link to a page showing how to sex a red-eared slider--different species, but the information pertains to your turtle as well.  Hope it helps!