🎩 Hat Size Converter
A 57 cm head wears a US 7⅛ fitted hat (UK 7), a size M, because fitted sizes are simply the head’s diameter in inches. Convert below, everything happens on your device.
Nearest standard size:
US fitted
7⅛
UK fitted
7
Letter
M
Head
57 cm
Head
22.4"
Between sizes? Choose the larger, hats shrink slightly and heads don't.
How to measure
- Wrap a soft tape (or string, then a ruler) around the head where a hat sits: mid-forehead, above the ears, around the widest back point.
- Keep it comfortably snug, one finger should slip beneath the tape.
- Read the circumference in cm or inches and enter it, the converter returns fitted and letter sizes.
- Between sizes? Choose the larger: hats shrink slightly with wear and weather; heads don’t.
The old-school "fitted" number is elegant: it's the head circumference in inches divided by π, effectively the diameter of your head, quoted in eighths. That's why a 22" head (56 cm) wears a size 7 (22 ÷ 3.1416 ≈ 7.0). UK fitted sizes run exactly ⅛ smaller than US for the same head, an artifact of different measuring conventions between hatmakers.
Hat size chart
| Head (cm) | Head (in) | US fitted | UK fitted | Letter |
|---|---|---|---|---|
| 52 | 20.5 | 6½ | 6⅜ | XS |
| 53 | 20.9 | 6⅝ | 6½ | XS |
| 54 | 21.3 | 6¾ | 6⅝ | S |
| 55 | 21.7 | 6⅞ | 6¾ | S |
| 56 | 22 | 7 | 6⅞ | M |
| 57 | 22.4 | 7⅛ | 7 | M |
| 58 | 22.8 | 7¼ | 7⅛ | L |
| 59 | 23.2 | 7⅜ | 7¼ | L |
| 60 | 23.6 | 7½ | 7⅜ | XL |
| 61 | 24 | 7⅝ | 7½ | XL |
| 62 | 24.4 | 7¾ | 7⅝ | XXL |
| 63 | 24.8 | 7⅞ | 7¾ | XXL |
| 64 | 25.2 | 8 | 7⅞ | XXL |
Frequently asked questions
How do I measure my head for a hat?
Tape around mid-forehead, above the ears and the widest point at the back, comfortably snug. Average adult heads run 54-58 cm (21¼–22¾ in); read the fitted size straight from the converter.
What do fitted hat sizes like 7¼ mean?
Head circumference in inches divided by π, the diameter, in eighths of an inch. 7¼ ≈ 22.8 in ≈ 58 cm circumference. Baseball fitted caps (New Era 59FIFTY) use exactly this scale.
What hat size is a size M?
Commonly 56-57 cm (US fitted 7-7⅛). Letters vary slightly by maker: S ≈ 54-55, M ≈ 56-57, L ≈ 58-59, XL ≈ 60-61 cm.
Are UK and US hat sizes the same?
Nearly, UK fitted sizes run ⅛ smaller than US for the same head (US 7⅛ = UK 7). Continental sizing skips the arithmetic and just uses centimeters.
Is this hat size converter private?
Yes. It runs entirely in your browser. Sizes and body measurements are never sent to a server, logged or stored, and the page works offline.