it's kinda like people, they grow at different rates, so do beardies but from what i've seen and read, and thru my on experiences with mine., i would say, from about 7 weeks to 3 months they are usually 7 to 12 inches long, then at 4 and 5 months , they seem to be 13 to 15 inches long, at least that's where mine are at 4 1/2 months. then when they'are adults , i believe they can be any where betwween 17 - 23 inches. this is not to say that they are smaller or larger. genetics plays a big part. i think if you see the parents of the babies, it's a good indicator what size your baby is looking at