Hat Size Converter
Head size in cm or inches to US, UK, EU and S/M/L hat sizes.
About this tool
Measure around your head, then enter the circumference in centimetres or inches, or enter a US fitted size you already know. The tool shows US, UK, European and letter sizes, with a full chart from 52 to 64 cm.
How hat sizes work
Measure with a soft tape about 1 cm above your eyebrows and ears, around the fullest part of the back of your head, snug but not tight. European hat sizes are simply the circumference in centimetres. US fitted sizes are the circumference in inches divided by ฯ (an imagined diameter), in eighths of an inch, and UK sizes run one-eighth smaller. So a 57 cm (22.4 in) head is a European 57, US 7 1/8 and UK 7, usually a medium. Letter sizes (S, M, L, XL) vary most between brands, so the chart's letters are a typical guide; adjustable caps usually fit about 55 to 60 cm. If you're between sizes, go up, because a hat that's slightly large can be padded, but one that's too tight can't be fixed. Honest limits: thick materials, sweatbands and hat shape change the fit, so check each brand's own size chart. The ring size converter and the shoe size converter are related.
Frequently asked questions
How do I measure my hat size?
Wrap a soft tape around your head about 1 cm above your eyebrows and ears, and read the circumference in cm or inches.
What hat size is 57 cm?
US 7 1/8, UK 7, European 57, typically a medium.
What is the difference between US and UK hat sizes?
UK sizes are one-eighth smaller than US for the same head: US 7 1/4 is UK 7 1/8.
What size is a one-size-fits-all cap?
Most adjustable caps fit about 55 to 60 cm (US 6 7/8 to 7 1/2).
Is my data sent anywhere?
No. Everything is calculated in your browser, and nothing is stored or sent.