Distressed Dad Hat - Otto Cap 104-1018 Hat Size Guide

Measure your head circumference with a non-stretchable measuring tape. Place the end of your  tape on your forehead and wrap the rest around the back of your head, keeping it 1″ (2.5 cm) above your ears. Pinch the spot where the tape meets the other end, lift the loop over your head, and note the measurement. Be as careful as possible to get the most precise measurement.
product measurement
 
A
B
C
D
inches
19 - 22
7
5
7 ¾
cm
48.3 - 56
12.7
6.6
19.7