I've been keeping track of my beardie's growth rate since I first got him (around the 1st of March). According to the rate of his growth, I've been estimating that he was born about December 10th. That means he would be turning 6 months in 4 days. Does this sound accurate? Here is the growth chart:
March 1st, 2017 - 8.5 inches (three months)
April 1st, 2017 - 10.5 inches (four months)
May 1st, 2017 - 12.5 inches (five months)
June 1st, 2017 - 14.5 inches (six months?)
My little guy is around 17 1/4 inches and 335 grams and I think he's around 6 months old. We got him from a petstore as well who had no real clue how old he was. He was about 7 1/2 inches and 20 grams then, so I just put his age at 7 weeks. They sell them pretty young at the major pet stores, my guy was the largest in the tank and he was still pretty small. He could very well be more around 5 months old, which would put him on par with my dragon. Just based off his size (which isnt the best indicator tbh) id put him around 5 months I guess. But you never know, one day you may think hes small then BAM he goes through a growth spurt and hes huge. Here is Zeke's growth chart: