Hat size chart and converter
Convert hat sizes between US fitted, UK fitted, EU and letter sizes, all from one head measurement. Enter your size or head circumference below.
Full hat size chart
| Letter | US fitted | UK fitted | EU | Head (cm) | Head (in) |
|---|---|---|---|---|---|
| XS | 6 5/8 | 6 1/2 | 53 | 53 | 20 7/8 |
| XS | 6 3/4 | 6 5/8 | 54 | 54 | 21 1/4 |
| S | 6 7/8 | 6 3/4 | 55 | 55 | 21 5/8 |
| S | 7 | 6 7/8 | 56 | 56 | 22 |
| M | 7 1/8 | 7 | 57 | 57 | 22 3/8 |
| M | 7 1/4 | 7 1/8 | 58 | 58 | 22 3/4 |
| L | 7 3/8 | 7 1/4 | 59 | 59 | 23 1/4 |
| L | 7 1/2 | 7 3/8 | 60 | 60 | 23 5/8 |
| XL | 7 5/8 | 7 1/2 | 61 | 61 | 24 |
| XL | 7 3/4 | 7 5/8 | 62 | 62 | 24 3/8 |
| XXL | 7 7/8 | 7 3/4 | 63 | 63 | 24 3/4 |
| XXL | 8 | 7 7/8 | 64 | 64 | 25 1/4 |
Hat sizing comes down to a single measurement, the circumference of your head, but the label put on that measurement changes by region and by hat type. Fitted caps in the United States use a numeric size that is really the diameter of the head in inches, the United Kingdom uses a similar numeric scale that rounds slightly differently, and most of Europe simply uses the head circumference in centimetres.
Casual hats use letter sizes from extra small to double extra large, which map to the same circumference bands. The chart below ties every one of these together, so once you know your head measurement you can buy a fitted cap, a beanie or a wide brim in any country with confidence.
Hat size questions
How do I know my hat size?
Measure the circumference of your head just above the ears and eyebrows, then match it to the chart. A 57 centimetre head is a US fitted 7 1/8, a UK 7, or a letter size M.
What is the difference between US and UK hat sizes?
Both are based on head diameter in inches but round differently, so the UK number is usually one eighth smaller than the US number for the same head. A US 7 1/8 is a UK 7.
What is the average hat size?
For adults the most common sizes are around 57 to 59 centimetres, which is a US fitted 7 1/8 to 7 3/8, or letter size M to L.
Do fitted hats stretch?
A little. Wool and cotton fitted caps give slightly with wear, so if you are between sizes and want a snug fit, the smaller size will loosen over time.
Last reviewed and updated on July 2, 2026. Conversion tables are checked against published international sizing standards.