Hat Sizes Converter
Convert hat sizes between US and UK fitted sizes, EU sizes and head circumference in centimeters or inches.
Sizes differ between brands and countries by up to half a size or more, so treat conversions as a starting point and check the brand's own chart and measure your head.
57 head circumference (cm) = 57 head circumference (cm)
Most used hat size units
Popular hat size conversions
- US hat sizes to head circumference (cm) 1 US = 7.979645 cm
- Head circumference (cm) to US hat sizes 1 cm = 0.1253189 US
- US hat sizes to UK hat sizes
- Head circumference (inches) to US hat sizes 1 in = 0.3183099 US
What is hat size?
Fitted hats are sized by head circumference. In Europe the size is simply the circumference in centimeters (57, 58, 59). US hat sizes are the circumference in inches divided by π, the diameter of an imaginary round head, which is why they come in eighths such as 7⅛ and 7⅜. UK sizes run one eighth below US sizes.
Measure around the head just above the eyebrows and ears, where the hat will sit.
All 4 hat size units
Sizes
Frequently asked questions
What is a 7 3/8 hat size in cm?
About 59 cm (23¼ inches).
What is the average hat size?
About 57–58 cm (US 7⅛–7¼) for adult men and 55–56 cm for women.