For accurate sizing, measure the circumference of the head from the center of the forehead all the way around where you want it to hit in the back of your head, and then back to the starting point on your forehead. This measure in inches is what I need to custom design your very own hat, so be sure to include it with your order(s).

These beanies are very stretchy, so sizing by age/estimating is usually just fine, particularly if it's a gift.