Hat Size Conversion Chart

How hat size conversion works

Hat sizes are written in three systems that all describe the same head. Fitted US sizes, such as 7 1/4, are the most precise, because they move in eighth size steps. Head circumference in cm or inches is the measurement behind every system, and letter sizes, such as M or L, are the roughest, because each letter covers two or three fitted sizes.

Conversion always starts from the circumference, not from a size you wore before. Two makers can print the same letter on hats that fit differently, but a 58 cm head is a 58 cm head wherever you measure it. Measure first, convert second, and you will get the same answer from any chart that uses the same general ranges.

Conversion chart table

The table above gives the same thirteen rows as the main size chart, so you can read any system across to the others. Find your head circumference in cm, then read left to the fitted US size or right to the letter size. The inches column is the same circumference written in inches, which helps when a shop lists inches only.

Worked conversion examples

Take a head of 56 cm. In the table, 56 cm sits in the row for US fitted 7 and letter size S, with 22 inches beside it. That is the size to look for first, and the letter S is what you would pick if the shop sells letter sizes only. A head of 61 cm sits in the row for US fitted 7 5/8 and letter size XL, with 23 1/2 inches beside it.

Take a head of 54 cm. That row is US fitted 6 3/4 and letter size S, with 21 1/4 inches beside it. Notice that 54 cm and 56 cm both sit in letter size S, which shows why letters are rough. If you only know your letter size, you still need the cm number to pick between the fitted sizes inside that letter.

Converting inches to cm

To turn inches into cm, multiply the inches figure by 2.54. A head of 22 1/2 inches is 22.5 times 2.54, which is about 57 cm, and the table puts 57 cm in the row for US fitted 7 1/8 and letter size M. To turn cm into inches, divide the cm figure by 2.54, so a 60 cm head is about 23.6 inches, which sits near the 23 inch row for US fitted 7 1/2.

Round to the nearest whole cm before you look at the table, because a fraction of a cm will not change the row. If your converted number lands exactly on a boundary, such as 58.5 cm, read the notes on between sizes before you pick a row. Our what to do when between hat sizes guide covers that choice.

Why conversions differ between makers

Conversions differ because makers grade their sizes differently and cut different crown shapes. One maker may grade its M to fit 57 cm heads and another may grade its M to fit 58 cm heads, and both can be right by their own chart. That is why a conversion table is general guidance, not a fixed rule, and why the brand chart matters more than any general table.

Our why clothing sizes vary between brands guide explains the grading reasons in more detail, and our how to convert clothing sizes between countries guide covers the same problem across clothing systems. For hats, the fix is the same in both cases: measure your head, use the general table for a starting size, then check the brand chart before you order.