I always feel like it can be hard to tell, considering many dragons are different sizes and different ages. My girl was on the shorter end than an “average” 3 month beardie - but some dragons are a larger size at 3 months! Regardless - this dragon you have appears super physically healthy at glance, so that’s always a good thing! I also reccomend keeping track of the length and weight - I think it must be cool to look back and see all that growth - and to compare it with others/or another of yours if you were to ever get another, to get an idea of their growth rate, etc. I wish I would have done that with my dragon!
It looks like a lot of websites are giving a 3 - 4 month length averages anywhere from 7 - 11 inches, but those ranges are not set in stone - I think they are mostly meant to give an idea - but with different dragons, different genetics, different care, etc - growth (length and weight) can be, well … different! I will say I think that this dragon definitely does *not* appear too small for a 3 month at all - in case if you ever had an worry over that!
Is that a boy or a girl? What is their name? Super gorgeous!