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Hat Size Converter
Measure around your head and get your fitted hat size in US, UK and European sizing plus the S–XXL letter size. You can also convert an existing size, such as US 7 1/4, into every other system.
Last updated:
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Measure around the head about 1 cm above the eyebrows and ears.
cm
Enter your values to see the result.
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How to use the Hat Size Converter
- Measure your head with a soft tape about 1 cm (1/2 in) above the eyebrows and ears, around the widest part at the back.
- Enter the measurement and choose cm or inches, or pick a size you already know.
- Read your US fitted size and the UK, EU and letter equivalents.
- If you are between sizes, take the larger one; a sizing strip can take up a little extra room.
- Check the chart or the kids' table for children's hats.
How hat sizes are calculated
US and UK fitted hat sizes come from the old hatter's practice of measuring the head's average diameter. In practice the size is the head circumference divided by π:
- US size = circumference in inches ÷ 3.1416, rounded to the nearest 1/8
- UK size = US size − 1/8
- EU size = circumference in centimeters
| Letter | Head (cm) | Head (in) | US | UK | EU |
|---|---|---|---|---|---|
| XS | 53–54 | 20 7/8–21 1/4 | 6 5/8–6 3/4 | 6 1/2–6 5/8 | 53–54 |
| S | 55–56 | 21 5/8–22 | 6 7/8–7 | 6 3/4–6 7/8 | 55–56 |
| M | 57–58 | 22 3/8–22 3/4 | 7 1/8–7 1/4 | 7–7 1/8 | 57–58 |
| L | 59–60 | 23 1/8–23 1/2 | 7 3/8–7 1/2 | 7 1/4–7 3/8 | 59–60 |
| XL | 61–62 | 24–24 3/8 | 7 5/8–7 3/4 | 7 1/2–7 5/8 | 61–62 |
| XXL | 63–64 | 24 3/4–25 1/8 | 7 7/8–8 | 7 3/4–7 7/8 | 63–64 |
How to measure your head for a hat
- Use a soft tailor's tape. If you only have a string or a phone charger cable, mark it and measure it against a ruler.
- Wrap it around the widest part of the head: across the forehead about 1 cm above the eyebrows, just above the ears and around the back.
- Keep it snug but not tight, with the tape level all the way round. Measure two or three times and use the largest reading.
- If you wear your hair up or thick, or will wear the hat over a headband, measure the way you will wear it.
Tips: felt and straw hats do not stretch much, so size up when in doubt and use a foam sizing strip to tighten a loose hat. Wool beanies and stretch-fit caps are forgiving by one size. Baseball caps labeled with fitted sizes (7 1/8, 7 1/4…) follow the US chart above.
Frequently asked questions
How do I convert head size to US hat size?
Divide your head circumference in inches by π (3.1416) and round to the nearest eighth. A 22 3/4 inch head gives 22.75 ÷ 3.1416 = 7.24, which is a US 7 1/4. In centimeters, divide by 2.54 first.
What size is a 7 1/4 hat in cm?
A US 7 1/4 fits a head circumference of about 57.9 cm, sold as European size 58. The UK equivalent is 7 1/8 and the letter size is M (medium).
What is the difference between US and UK hat sizes?
UK hat sizes run one eighth smaller in number than US sizes for the same head. A UK 7 is a US 7 1/8, both fitting about 57 cm.
What are European hat sizes?
European hat sizes are simply the head circumference in centimeters, so a 58 fits a 58 cm head. That makes EU sizing the easiest to check with a tape measure.
What is the average adult hat size?
Most adults measure between 55 and 60 cm (21 5/8 to 23 5/8 in), US sizes 6 7/8 to 7 1/2. Medium (57–58 cm, US 7 1/8–7 1/4) is the most common size, and men's heads average slightly larger than women's.
How do adjustable S/M and L/XL hats fit?
Stretch-fit and adjustable caps cover two letter sizes. S/M typically fits about 55–58 cm (US 6 7/8–7 1/4) and L/XL about 59–62 cm (US 7 3/8–7 3/4). Check the brand's chart because ranges vary.
What hat size does a baby or child wear?
Baby and kids' hats are usually sold by age: about 35–41 cm for 0–3 months, 43–46 cm for 6–12 months, 46–48 cm for 1–2 years and 48–51 cm for 2–4 years. Children vary a lot, so measuring is more reliable than age.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.
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