We suggest using a soft tape measure to measure the circumference of you or your child's head before ordering.
Camp The Label Wool Felt Hats are sized as follows:
Kids (50cm to 53cm) - avg. fit is for 2-4 year olds.
XS (53cm to 55cm) - avg fit is 4-7 year olds. (by ages 5/6 the skull has grown to over 90% of the adult size)
S/M (55cm to 57cm)
M/L (57cm)
XL - *More sizes coming soon

The most common hat size for women is a S/M (57cm). If you consider yourself to have a "small head" we suggest going with size 55cm. 

Camp The Label Beanies are sized as follows

Infant - Avg for babies age newborn-3 years old

Youth - Avg. for children 3-5

Adult Small/Med. - Suggested for those with head circumference of 55-57cm

Adult Large/XL - Suggested for those with a head circumference of 58+

NOTE: To wear "fisherman style" aka double folded, please size up.