Hat Size Converter – US, UK, CM & Inches Hat Size Chart
Hat Size Converter
Free hat size converter – type a value into any field to instantly convert head measurements into standard hat sizes.
Use this free hat size converter to turn your head measurement into US and UK hat sizes, or convert between cm, inches, US and UK.
Quick answer
To find your hat size, measure your head circumference and use this hat size converter. The US hat size equals the circumference in inches ÷ π (3.14159), and the UK size is 1/8 smaller than the US size. Example: a 57 cm (22.44 in) head is about US 7 1/8 and UK 7. Type into any field and all sizes update instantly.
Table of Contents
Hat sizes are confusing because every region uses a different system. American fitted caps and fedoras use fractional sizes like 7 1/4, British hats run one-eighth smaller, and European brands simply use your head circumference in centimetres. Order the wrong size online and the hat either perches on top of your head or slides over your eyes.
Our free hat size converter solves that in seconds. Enter a US size, UK size, or your head measurement in cm or inches, and the other three values are calculated instantly. A standard sizing matrix inside the tool shows the most common sizes at a glance.
How to Measure Your Head for a Hat
- Use a soft tailor’s tape measure. If you only have string, mark it and measure it against a ruler.
- Wrap the tape around your head about 1 cm (1/2 in) above your eyebrows and the tops of your ears, over the widest part at the back.
- Keep the tape snug but not tight, and level all the way round.
- Measure two or three times and use the largest result.
- If you fall between two sizes, choose the larger one – a little foam sizing tape fixes a slightly loose hat, but nothing fixes a tight one.
Hat Size Conversion Formula
- US size = head circumference in inches ÷ π
- UK size = US size − 1/8
- Centimetres = inches × 2.54 (European sizes use cm directly)
Worked example: a head measuring 58.85 cm is 58.85 ÷ 2.54 = 23.17 in. 23.17 ÷ 3.14159 ≈ US 7 3/8, which is UK 7 1/4 and European size 59.
How to Use the Hat Size Converter
Find your size in three quick steps.
Step 1: Enter Your Head Measurement
Type your head circumference into Circumference (CM) or Circumference (Inches). For example, enter 57 cm and the hat size converter shows US 7.143 (about 7 1/8), UK 7.018 (about 7) and 22.44 inches.
Step 2: Or Convert Between US and UK Sizes
Already know a size from a label? Type it into US Size or UK Size using decimals – 7 3/8 is 7.375. The tool returns UK 7.25 (7 1/4), 58.85 cm and 23.17 in.
Step 3: Check the Standard Sizing Matrix
Compare your result with the Standard Sizing Matrix, which pairs US sizes with UK sizes, centimetres and letter sizes such as Medium and Large. Click Clear Fields to start over.
Hat Size Chart: US, UK, CM and Inches
| US size | UK size | Head (cm) | Head (in) | Letter size |
|---|---|---|---|---|
| 6 3/4 | 6 5/8 | 53.9 | 21.2 | XS |
| 6 7/8 | 6 3/4 | 54.9 | 21.6 | S |
| 7 | 6 7/8 | 55.8 | 22.0 | S / M |
| 7 1/8 | 7 | 56.8 | 22.4 | M |
| 7 1/4 | 7 1/8 | 57.8 | 22.8 | M / L |
| 7 3/8 | 7 1/4 | 58.9 | 23.2 | L |
| 7 1/2 | 7 3/8 | 59.8 | 23.6 | L / XL |
| 7 5/8 | 7 1/2 | 60.8 | 24.0 | XL |
| 7 3/4 | 7 5/8 | 61.8 | 24.4 | XXL |
Letter sizes vary between brands, so always check the maker’s own chart when one is available.
Fraction to Decimal Guide for US Hat Sizes
The hat size converter uses decimals. Convert fractions like this:
| Fraction | Decimal |
|---|---|
| 1/8 | 0.125 |
| 1/4 | 0.25 |
| 3/8 | 0.375 |
| 1/2 | 0.5 |
| 5/8 | 0.625 |
| 3/4 | 0.75 |
| 7/8 | 0.875 |
Tips for Choosing the Right Hat Size
- Fitted caps follow the US fractional system exactly – size accuracy matters most here.
- Fedoras and felt hats can be adjusted slightly with sizing tape inside the sweatband.
- Beanies and snapbacks are usually one-size, but a measurement still helps if a brand offers S/M and L/XL.
- Kids’ hats use the same formula; children’s heads often measure 48–54 cm.
Need other size conversions? Try our Bra Size Converter or the Torque Unit Converter for workshop units.
Frequently Asked Questions
How do I know my hat size?
Measure around your head 1 cm above your eyebrows and ears. Divide the inches by 3.14159 for your US size, or enter the measurement in this hat size converter.
What is the difference between US and UK hat sizes?
UK hat sizes are 1/8 smaller than US sizes. A US 7 1/4 is a UK 7 1/8.
What hat size is 58 cm?
58 cm is about US 7 1/4 (7.27) and UK 7 1/8. It is usually sold as Medium/Large.
What hat size is 22 inches?
A 22-inch head is about US 7 and UK 6 7/8, or 56 cm in European sizing.
Should I size up if I am between hat sizes?
Yes. Choose the larger size and add sizing tape if needed. A hat that is too tight is uncomfortable.
Is the hat size converter free?
Yes. It is free, needs no sign-up and works on any phone or computer.