The measurements on the size chart are body measurements.
FIT TIPS
* If you're on the borderline between two sizes, order the smaller size for a tighter fit or the larger size for a looser fit.
* OS = One Size.
HOW TO MEASURE
Measure the circumference of your head using a measuring tape. Wrap it around your head at the point where the hat will sit (about an inch/2.5cm above your eyebrows).
| SIZE | US - MEN'S | US - WOMEN'S | US KIDS | UK | EU |
| XS | 13C-3Y | 31-35 | |||
| S | 4-6 | 3Y-5Y | 2-5 | 34-38 | |
| M | 6-8 | 6-10 | 5Y-7Y | 5-8 | 38-42 |
| L | 8-12 | 10-13 | 8-11 | 42-46 | |
| XL | 12-15 | 11-14.5 | 46-50 |
HATS AND HEADWEAR
| Nike Hat Size | Head Size | Alpha Size | Swosh Flex | Unisex | Women's | Dual Size Unisex | Women's |
| 6 1/2 | 20 1/2 | XS | S | ||||
| 6 5/8 | 20 7/8 | XS/S | XS | S OS | S/M | ||
| 6 3/4 | 21 1/8 | XS | XS/S | XS S OS | S OS | S/M | |
| 6 7/8 | 21 1/2 | XS/S S/M | XS S OS | S OS | XS/S | ||
| 7 | 21 7/8 | S | XS/S S/M | XS S OS | S OS | M/L | |
| 7 1/8 | 22 1/4 | S/M M/L OS | XS S OS | S OS | S/M | ||
| 7 1/4 | 22 5/8 | M | S/M M/L OS | S OS | OS L | L/XL | |
| 7 3/8 | 23 | M/L L/XL OS | S OS XL | OS L | M/L | ||
| 7 1/2 | 23 1/2 | L | M/L L/XL OS | OS XL | L | ||
| 7 5/8 | 23 7/8 | L/XL XL/XXL | OS XL | L | |||
| 7 3/4 | 24 1/4 | XL | L/XL XL/XXL | XL | L | ||
| 7 7/8 | 24 5/8 | XL | L | XL/XXL | |||
| 8 | 25+ | XL |