How to convert hat sizes
Hat size conversion chart
Letter sizes (S–XXL), US numeric sizes and the head circumferences they fit, in centimetres and inches.
| Size | US number | Head (cm) | Head (in) |
|---|---|---|---|
| S | 6¾ | 54–55 | 21.3–21.7 |
| M | 7 | 55–57 | 21.7–22.4 |
| L | 7¼ | 57–59 | 22.4–23.2 |
| XL | 7½ | 59–61 | 23.2–24 |
| XXL | 7¾ | 61–63 | 24–24.8 |
Hats should fit snugly without pressure. If you are between sizes, most people prefer the larger size, since a hat that is too small is uncomfortable.
How letters, numbers and centimetres relate
Hat sizing expresses the same head circumference three ways: a letter range (S to XXL), a US numeric size that counts head circumference in inches (for example 7 ⅛), and the circumference itself in centimetres or inches. This converter maps all three onto the same size row.
How to use this hat size converter
Choose the scale you know — letter, US numeric or a head measurement — and the matching row appears with every equivalent at once. The chart shows all sizes so you can compare the letters against your own head circumference.
How to measure your head for a hat
Wrap a tape measure around your head about a finger’s width above the eyebrows and ears — the point where a hat naturally sits — keeping it level. Read the circumference in centimetres; that single number is all you need.
Tips for a comfortable hat fit
Different hat styles sit at different points on your head and may feel looser or tighter. If a style runs small (many structured caps do), going one numeric size up is a safe choice.
Frequently asked questions
How do I convert US numeric hat sizes to cm?
The US number is simply head circumference in inches, so multiplying by 2.54 gives centimetres — a 7 fits about a 56 cm head. The chart already shows both so you can cross-check.
Which letter size am I?
Compare your head circumference to the ranges: roughly 54–55 cm is S, 56–57 M, 58–59 L and 60–61 XL, with XXL from about 62 cm. Individual brands grade slightly differently, so treat letters as approximate.
Do one-size hats use the same scale?
Most “one size” hats are sized for an average head of about 56–58 cm and stretch to fit a range around it. If your head is above about 60 cm, look for an XL or adjustable style instead.
Should I size up or down if I am between two sizes?
Size up. Hats do not stretch much, and a slightly loose hat can be padded or adjusted, while one that is too small gives headaches. Many structured caps also shrink a little with wear.
Do children’s hats use the same letters?
Children’s hats are sized separately (often by age or a smaller numeric range), so adult S–XXL letters do not apply. Use the child’s head circumference in cm against a children’s chart.