How do I measure my head for a hat?

Run a soft tape around your head about a centimetre above the ears and across the middle of the forehead, where the hat band will sit. Keep it snug but not tight, and take the measurement twice to be sure.

What size hat is 58 cm?

58 cm is a US 7 1/4, a UK 7 1/8, a European 58 and a medium in alphabetic sizing. It is the single most common adult men's size.

Why are hat sizes numbers like 7 1/4?

The number is the diameter of your head in inches, not the circumference — circumference divided by π. Hatters historically sized blocks by diameter, and the eighth-inch steps stuck.

How much smaller is a UK hat size than a US one?

Exactly one eighth. The two systems measure the same diameter but start their scales an eighth apart, so US 7 1/2 equals UK 7 3/8.

Should I size up or down between two hat sizes?

Up. A snug hat can be padded down with sizing tape in a couple of minutes, and felt and wool relax with wear, but a hat that is genuinely too small never becomes comfortable.

Hat Size Converter

Turn a head measurement into a fitted hat size in every system, or work backwards from a size you already know fits.

The Hat Size Converter runs entirely in your browser. Your measurements stay on your device.

Open the Clothing Size Converter

About Hat Size Converter

Every hat system starts from one measurement: the circumference of your head about a centimetre above the ears and across the middle of the forehead. A US fitted size is that circumference divided by π — the diameter of the circle in inches — rounded to the nearest eighth, which is why fitted caps come in sizes like 7 1/4 rather than round numbers. A UK size is one eighth smaller for the same head, a difference that catches people out when ordering from abroad. European sizes skip the arithmetic entirely and use the centimetre figure. Enter whichever number you have — a measurement, a US size or an EU size — and read all of them together, along with the S/M/L band retailers use.

Features

Convert from centimetres, inches, a US fitted size or an EU size
US and UK fitted sizes written as proper eighths, e.g. 7 1/4
European centimetre sizing and S/M/L bands
Full chart from 52 to 64 cm with your row highlighted
Warns when a measurement lands between two eighths
Copyable summary for an order note
Works in both metric and imperial measurements
Conversions run in your browser

How to use the Hat Size Converter

Measure around your head above the ears with a soft tape
Choose whether you are entering centimetres, inches or a size
Read the US, UK, EU and alphabetic equivalents
Check the chart if you are between two sizes

Example

Input

58 cm head circumference

Output

22.83 in · US 7 1/4 · UK 7 1/8 · EU 58 · size M

58 ÷ 2.54 ÷ π = 7.27 inches of diameter, which rounds to the nearest eighth.

Common errors & troubleshooting

The UK size looks a full size smaller than expected. — It is one eighth smaller by definition, not by accident. A US 7 1/4 is a UK 7 1/8 for the same head, so ordering the same number from a British maker gives you a hat that is slightly too tight.
The measurement falls exactly between two sizes. — Take the larger one. Wool and felt hats give a little as they are worn and can be stretched; a hat that is too small can only be lived with.
A stated S/M/L does not match the measurement. — Alphabetic sizing has no standard behind it and varies by brand and by style. Use the centimetre figure whenever the maker publishes one, and treat S/M/L as a rough guide.

Frequently asked questions

How do I measure my head for a hat?: Run a soft tape around your head about a centimetre above the ears and across the middle of the forehead, where the hat band will sit. Keep it snug but not tight, and take the measurement twice to be sure.
What size hat is 58 cm?: 58 cm is a US 7 1/4, a UK 7 1/8, a European 58 and a medium in alphabetic sizing. It is the single most common adult men's size.
Why are hat sizes numbers like 7 1/4?: The number is the diameter of your head in inches, not the circumference — circumference divided by π. Hatters historically sized blocks by diameter, and the eighth-inch steps stuck.
How much smaller is a UK hat size than a US one?: Exactly one eighth. The two systems measure the same diameter but start their scales an eighth apart, so US 7 1/2 equals UK 7 3/8.
Should I size up or down between two hat sizes?: Up. A snug hat can be padded down with sizing tape in a couple of minutes, and felt and wool relax with wear, but a hat that is genuinely too small never becomes comfortable.

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