US to UK to EU hat size chart
American hat sizes are the head diameter in inches. British sizes use the same idea but run ⅛ smaller, so a US 7 ¼ is a UK 7 ⅛. European and French sizes are the circumference in centimetres. Japanese sizes also use centimetres.
| US | Letter | Inches | cm | UK | EU/FR |
|---|---|---|---|---|---|
| 6 ¼ | – | 19 ⅝ | 50 | 6 ⅛ | 50 |
| 6 ⅜ | – | 20 ⅛ | 51 | 6 ¼ | 51 |
| 6 ½ | XS | 20 ½ | 52 | 6 ⅜ | 52 |
| 6 ⅝ | XS | 20 ⅞ | 53 | 6 ½ | 53 |
| 6 ¾ | S | 21 ¼ | 54 | 6 ⅝ | 54 |
| 6 ⅞ | S | 21 ⅝ | 55 | 6 ¾ | 55 |
| 7 | M | 22 | 56 | 6 ⅞ | 56 |
| 7 ⅛ | M | 22 ½ | 57 | 7 | 57 |
| 7 ¼ | L | 22 ⅞ | 58 | 7 ⅛ | 58 |
| 7 ⅜ | L | 23 ¼ | 59 | 7 ¼ | 59 |
| 7 ½ | XL | 23 ⅝ | 60 | 7 ⅜ | 60 |
| 7 ⅝ | XL | 24 | 61 | 7 ½ | 61 |
| 7 ¾ | XXL | 24 ⅜ | 62 | 7 ⅝ | 62 |
| 7 ⅞ | XXL | 24 ¾ | 63 | 7 ¾ | 63 |
| 8 | 3XL | 25 ¼ | 64 | 7 ⅞ | 64 |
| 8 ⅛ | 3XL | 25 ⅝ | 65 | 8 | 65 |
| 8 ¼ | 3XL | 26 | 66 | 8 ⅛ | 66 |
Why US and UK sizes differ
Both systems divide circumference by pi, but British hatters traditionally measured the inside of the hat block, which is slightly smaller than the head. The result is a consistent ⅛ inch offset. If you buy from a UK hatter and know your US size, subtract ⅛.