Hat Size Calculator
Measure around your head and convert it to a US/UK fitted hat size, EU centimetres and S/M/L.
Find your hat size
How to measure
Wrap around your head
Run a soft tape around the widest part โ about 1 cm above the ears and across the mid-forehead.
Keep it level and snug
Not tight; the tape should sit where a hat band would. Take the measurement twice.
Read your size
Fitted hats use the US/UK number; many casual hats use S/M/L; European hats use the cm number.
Between sizes?
Size up and use a hat-sizing foam tape inside the band to fine-tune.
Baseball and fitted caps in true sizes.
View on Amazon โFoam tape to take a loose hat down a touch.
View on Amazon โFrequently asked questions
What hat size is a 57 cm head?
A 57 cm head is about a US 7โ , UK 7, EU 57 โ a Medium in S/M/L sizing.
How is hat size calculated?
Fitted hat size is your head circumference in inches divided by pi. A 22-inch (56 cm) head gives a size 7.
How this is calculated
The US/UK fitted hat size is the head circumference in inches divided by pi (so a 22-inch head is a size 7). UK sizes run about โ smaller than US. EU sizes are simply the head circumference in centimetres. S/M/L bands follow the common cm ranges.
Sources: Standard fitted-hat formula (size = circumference in inches รท ฯ), cross-checked retailer charts 2026.