๐ Fashion & Sizing
Hat Size Calculator
A hat is sized by head circumference, and the US number is that circumference divided by pi โ which is why a 22 inch head is a size 7. Measure around the widest part of your head, about a centimetre above the ears.
How it works
Head circumference
Measurement unit
Preferred fit
US hat size
UK hat size
Metric size (cm)
Letter size
Frequently asked questions
How do I use the Hat Size Calculator?
Fill in the fields above โ the result recalculates instantly as you type. Everything runs in your browser, so the values you enter are never collected or stored.
Is this calculator free?
Yes. It is completely free, requires no account, and works on phones, tablets and desktops.