hat size chart & calculator
Enter your head measurement to get your US fitted, UK, European and letter size, plus the right cap size for fitted and stretch-fit styles.
fashion law journal · tools deskupdated 25 sep 2026adult sizes
Quick answer: measure around your head about 1 cm above your ears and eyebrows. European hat size is that number in centimetres. US hat size is the measurement in inches divided by π, so a 57 cm (about 22½ in) head is a US 7⅛, a UK 7 and a size M.
Use a soft tape measure. Keep it level, about a finger’s width above your ears and across the middle of your forehead. Measure twice.
No tape? Wrap a piece of string around your head, mark it, and measure the string against a ruler.
hat size conversion chart
| head (cm) | head (in) | US fitted | UK | EU | letter | stretch cap |
|---|
Stretch cap ranges follow the common S/M, M/L and L/XL bands used by most fitted-flex caps. Individual brands can shift by a size.
between two sizes?
- Felt, fedoras and fitted caps: size up. A slightly loose hat can be tightened with a foam sizing strip, but a tight one gives you a headache.
- Beanies and knits: size down, or pick one size. They stretch.
- Sun and straw hats: size up. Straw has almost no give.
- Long or thick hair: measure with your hair styled the way you’ll wear the hat.
how a hat should fit
The brim should sit about a finger’s width above your eyebrows and ears. You should be able to slide one finger between the band and your forehead.
If the hat leaves a red line after ten minutes, it’s too small. If it moves when you turn your head quickly, it’s too big.
hat size questions
How do I convert head size to hat size?
For European sizing, your head circumference in centimetres is the size. For US fitted sizing, divide the circumference in inches by 3.14 and round to the nearest eighth. UK sizes run one eighth smaller than US.
What is the average hat size?
For adults it’s around 57 to 58 cm, which is a US 7⅛ to 7¼ or a size M. Heads vary a lot, so measure rather than guess.
What size is a fitted cap?
Fitted caps use US hat sizes (7, 7⅛, 7¼ and so on). Stretch caps use S/M, M/L and L/XL bands that each cover about three US sizes.
Are UK and US hat sizes the same?
No. The UK size is usually one eighth smaller than the US size for the same head, so a US 7¼ is a UK 7⅛.
How do I make a big hat smaller?
Add a foam hat-sizing tape inside the sweatband. It can take a hat down by up to one size.
Conversions use standard hatter sizing. Brands vary, so check the maker’s own chart for made-to-measure pieces. More from FLJ: ring size chart · color analysis quiz.