International conversions Nov 17, 2026 3 min read
Hat Size Conversion: US to EU (Inches to cm)
US hats use 6 7/8 to 8 fractional sizing (= circumference / pi). EU uses straight head circumference in cm.
The Chart
| US Size | Inch Circ. | EU (cm) | S/M/L |
|---|---|---|---|
| 6 5/8 | 20.75 | 53 | XS |
| 6 3/4 | 21.25 | 54 | S |
| 6 7/8 | 21.625 | 55 | S |
| 7 | 22 | 56 | M |
| 7 1/8 | 22.375 | 57 | M |
| 7 1/4 | 22.75 | 58 | L |
| 7 3/8 | 23.125 | 59 | L |
| 7 1/2 | 23.5 | 60 | XL |
| 7 5/8 | 23.875 | 61 | XL |
| 7 3/4 | 24.25 | 62 | 2XL |
| 7 7/8 | 24.625 | 63 | 2XL |
| 8 | 25 | 64 | 3XL |
FAQs
Why fractional US hat sizes?
US hat size = head circumference (inches) / pi (3.14). 22 inch circumference / 3.14 = 7. Used since the 1900s for fitted hats; New Era still uses this for fitted MLB caps.
Why does EU use cm directly?
More precise. cm circumference is just a measurement, no math. Modern hats increasingly label both: 7 1/4 (US) / 58 cm (EU).
Need this on your store?
Tailor Size Guide ships pre-built size charts for Shopify.