US hat size to UK and EU
Useful when a foreign store lists hat sizes as fractions.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter us size.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Circumference (in) = US size × π, circumference (cm) = inches × 2.54, UK = US − 1/8, EU = circumference in cm, rounded.
Example
Inputs: US size = 7. Result: UK size: 6 7/8; EU size (ISO): 56 cm; Head circumference: 55.9 cm.
Limits and caveats
- Letter sizes such as S, M and L vary by brand.
- Some brands round the EU size to half centimeters.
Questions about this tool
What is US size 7 in cm?
About 55.9 cm around, which is EU 56 and UK 6 7/8.
Why is the US size a small number like 7?
It is roughly the head diameter in inches, the circumference divided by π.
How far apart are two sizes?
Each 1/8 step adds about 1 cm of circumference (π × 1/8 in).