Measuring is key to getting the perfect Go girl fit.
We measure where the headbands sits and then subtract 2". Start behind the neck, go up behind the ears and measure at the top of the forehead at the hairline. Subtract 2" and you have your Go girl! Headband size.
Generally, if I were to advise you on sizes based on age:
17" fits your average 3 year old.
18" fits 4-8 year olds
19" fits 9-12 year olds (call this a Small adult or the Tween growing phase)
20" fits your average adult size head (just call this a Medium adult)
21" fits a slightly larger adult head (call this a Large adult)
22" fits someone who says "Headbands NEVER fit me!" (I hear this a lot!)
Many times moms and daughters (teens and older) have the same size head.