Hat Sizes
Accessories · 6 specs
Direct Answer
Hat and cap sizes are derived directly from head circumference measured one centimeter above the ears. Sized in traditional fitted fractions (6-1/2 to 8-1/4) and alpha sizes (S to 3XL), the US numerical size represents head diameter in inches calculated by dividing circumference in centimeters by 8.
Source: Traditional US/UK Hat Sizing Standards / Headwear Association · Last reviewed Aug 28, 2026
Specs
| Governing Standards | Headwear Association / Traditional US/UK Sizing Standard |
| Measurement Location | 1.0 cm (0.5") above ears across widest point of forehead |
| US Sizing Formula | US Hat Size = Head Circumference in cm ÷ 8 (e.g., 56 cm ÷ 8 = Size 7) |
| Fitted Sizing Range | 6-1/2 (20.5" / 52 cm) to 8-1/4 (26.0" / 66 cm) |
| Alpha Sizing Scale | Small (54–55 cm), Medium (56–57 cm), Large (58–59 cm), XL (60–61 cm), XXL (62–63 cm) |
| US vs UK Hat Size Offset | UK Hat Size is approximately 1/8 size smaller than US (e.g., US 7-1/4 = UK 7-1/8) |
Fitted Hat & Cap Size Conversion Matrix
| Alpha Size | Fitted US Size | Fitted UK Size | Head Circumference (cm) | Head Circumference (Inches) |
|---|---|---|---|---|
| XS | 6-1/2 | 6-3/8 | 52.0 cm | 20.50" |
| XS | 6-5/8 | 6-1/2 | 53.0 cm | 20.88" |
| S | 6-3/4 | 6-5/8 | 54.0 cm | 21.25" |
| S | 6-7/8 | 6-3/4 | 55.0 cm | 21.63" |
| M | 7.0 (7) | 6-7/8 | 56.0 cm | 22.00" |
| M | 7-1/8 | 7.0 | 57.0 cm | 22.50" |
| L | 7-1/4 | 7-1/8 | 58.0 cm | 22.88" |
| L | 7-3/8 | 7-1/4 | 59.0 cm | 23.25" |
| XL | 7-1/2 | 7-3/8 | 60.0 cm | 23.63" |
| XL | 7-5/8 | 7-1/2 | 61.0 cm | 24.00" |
| XXL | 7-3/4 | 7-5/8 | 62.0 cm | 24.38" |
| XXL | 7-7/8 | 7-3/4 | 63.0 cm | 24.75" |
| 3XL | 8.0 (8) | 7-7/8 | 64.0 cm | 25.25" |
| 3XL | 8-1/4 | 8-1/8 | 66.0 cm | 26.00" |
How to Measure Head Circumference
- Wrap a flexible tailor's tape measure around your head 1 cm (about 1/2 inch) above your ears and eyebrows, passing over the occipital bump at the back of your skull.
- Hold the tape comfortably snug — not pulled tight.
- If your measurement falls between two sizes, round UP to the larger size (hat sizing reduction tape can easily be placed inside the sweatband for a custom fit).