http://how-old.net
It also guesses your gender.
You will find that it will give you different ages for pictures taken of you around the same time. Obviously it's not perfect.
But it's pretty good, given that it's an automated machine.
It also verified something I thought about my own aging.
Up until about age 35, people usually thought I was a lot younger than my actual age. Starting at 36, I seemed to rapidly "catch up" and then was getting guessed only slightly younger than my actual age -- something which still persists today. Strangers usually put me at 37-41 (I'm 43), whereas I was routinely guessed as being in my 20s when I was 34-35.
The "how old" machine indeed puts most pics of me from 2007 and before in the 25-29 age range, and pictures from 2008-2015 in the 37-42 age range, with little in between.
Give it a try for yourself.