It isn't quite so simple with reptiles, as their growth is so dependent on many different factors, including temperature.
A picture, and a weight (grams please) would give you at least a starting point. My female veiled is 45g. I just read jannb's laying bin post, and her female, after laying eggs, was about 140g. From this I'm assuming that mine is not close to being adult yet even though she's nine months old.