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.
Where these numbers come from
Every row in this chart is anchored to the circumference of the head in centimetres. The EU number is the head circumference in whole centimetres. The US and UK fitted numbers are eighths of an inch of head diameter, which is the circumference divided by pi, which is why they come out as fractions like 7 1/8 rather than round numbers.
What is not standardised. We know of no published international standard for hat sizes. Every column here is a convention derived from head circumference, which is why the circumference column is the one to trust.
Reviewed by Jamey Weber, last checked August 5, 2026. Found an error? Report it and it gets fixed in the changelog. See also the full methodology.
Last reviewed and updated on August 5, 2026. Conversion tables are checked against published international sizing standards.