Hat Size Chart: US, UK, and Head Circumference (cm/inches)
Convert hat sizes between US, UK, and head circumference in centimeters and inches, with instructions for measuring your head size.
Head Circumference (cm): 53.3
| US/UK Hat Size | Head Circumference (cm) | Head Circumference (in) | S/M/L |
|---|---|---|---|
| 6 5/8 | 53.3 | 21 | XS |
| 6 3/4 | 54.6 | 21.5 | S |
| 6 7/8 | 55.9 | 22 | S |
| 7 | 56.8 | 22.4 | M |
| 7 1/8 | 57.8 | 22.8 | M |
| 7 1/4 | 58.7 | 23.1 | L |
| 7 3/8 | 59.7 | 23.5 | L |
| 7 1/2 | 60.6 | 23.9 | XL |
| 7 5/8 | 61.6 | 24.3 | XL |
| 7 3/4 | 62.5 | 24.6 | XXL |
| 7 7/8 | 63.5 | 25 | XXL |
How to Measure
Wrap a flexible tape measure around your head about 1.5cm above your eyebrows and ears, at the widest part of your head, keeping the tape level. Measure in centimeters for the most direct match to the chart, since US/UK hat sizes are themselves derived from head circumference divided by π (the hat size number is approximately the diameter, in inches, of the head's circumference).
Notes
US and UK hat sizes use the same numbering, derived historically from head circumference divided by π — this is why the numbers (6 5/8, 7, 7 1/4...) look unusual compared to a clean centimeter or inch measurement. Letter sizes (S/M/L) vary more between brands than numeric sizes, so use the numeric or centimeter measurement when available.
Frequently Asked Questions
Source: Compiled from common US/UK millinery size standards · see our methodology