How to find a hat size
Measure the head, choose a fit, then read the matching system.
Measure the head
Use a soft tape around the widest point, above the ears and across the forehead.
Choose a fit
A comfortable fit adds about half a centimetre; a loose fit adds about one.
Compare systems
Use the US, UK and EU rows to match the brand size chart.
What does this tool do?
Hat sizing is based on head circumference, with the US system describing the circumference in inches divided by pi. This calculator converts a measurement into US fractions, UK sizes and the metric EU size.
The Formula
US size = circumference (in) ÷ π, rounded to 1/8; UK = US − 1/8; EU = circumference (cm)Frequently Asked Questions
How should I measure my head?
Wrap a soft tape around the widest part, about one centimetre above the ears and across the mid-forehead. Keep it level and snug without pulling tight.
What if I am between sizes?
Choose the larger size for comfort, especially with thick hair or a relaxed fit preference. Adjustable bands can also bridge a small gap.