Ring Size Converter
Convert ring sizes between US, UK, EU, Japan and the physical size in millimetres: inner diameter and circumference. Enter a size in any system and you'll see the rest. There's a full chart, plus a quick note on how to measure. It's free and instant.
Match a ring size across countries or work straight from a measurement in millimetres. Convert US to UK, EU to Japan, or turn an inner diameter into a size, which is ideal for buying abroad or ordering a surprise from a ring that already fits. Enter one value and read every system.
- Exact, standard factors
- 100% free
- No sign-up, no app
- Instant as you type
- Works offline after first load
Ring size chart
| US | UK | EU | JP | Ø mm | Circ. mm |
|---|---|---|---|---|---|
| 3 | F | 44 | 4 | 14 | 44 |
| 3.5 | G | 45 | 5 | 14.4 | 45.2 |
| 4 | H½ | 46 | 7 | 14.8 | 46.5 |
| 4.5 | I½ | 48 | 8 | 15.2 | 47.8 |
| 5 | J½ | 49 | 9 | 15.7 | 49.3 |
| 5.5 | K½ | 51 | 10 | 16.1 | 50.6 |
| 6 | L½ | 52 | 12 | 16.5 | 51.8 |
| 6.5 | M½ | 53 | 13 | 16.9 | 53.1 |
| 7 | N½ | 54 | 14 | 17.3 | 54.3 |
| 7.5 | O½ | 56 | 15 | 17.7 | 55.6 |
| 8 | P½ | 57 | 16 | 18.1 | 56.9 |
| 8.5 | Q½ | 58 | 17 | 18.5 | 58.1 |
| 9 | R½ | 59 | 18 | 18.9 | 59.4 |
| 9.5 | S½ | 61 | 19 | 19.4 | 60.9 |
| 10 | T½ | 62 | 20 | 19.8 | 62.2 |
| 10.5 | U½ | 63 | 22 | 20.2 | 63.5 |
| 11 | V½ | 65 | 23 | 20.6 | 64.7 |
| 11.5 | W½ | 66 | 24 | 21 | 66 |
| 12 | Y | 67 | 25 | 21.4 | 67.2 |
| 12.5 | Z | 68 | 26 | 21.8 | 68.5 |
| 13 | Z+1 | 70 | 27 | 22.2 | 69.7 |
To measure at home, wrap a strip of paper or string around the base of your finger, mark where it overlaps, and measure that length in millimetres. That is the circumference. Or measure the inner diameter of a ring that already fits. Sizes vary slightly by maker, so treat the result as the nearest standard size.
How to use it
- 1
Choose the system
Pick the system your size is in: US, UK, EU, Japan, or a measurement in millimetres.
- 2
Enter your size
Type a letter for UK sizes, or a number for the rest.
- 3
Read the equivalents
See every other system plus the inner diameter and circumference in mm.
When it comes in handy
Buying a ring abroad
Match a size shown in one country's system to the one your jeweller uses.
Planning a surprise
Measure a ring that already fits and read off the size to order another.
Working in millimetres
Get the exact inner diameter a jeweller needs when they size by measurement.
Instant, exact & 100% in your browser
The conversion runs right here in your browser using exact, standard factors. Nothing you type is sent to a server, there is no sign-up and no limit, and once the page has loaded it keeps working even with no connection.
Frequently asked questions
- How do I measure my ring size at home?
- Wrap a strip of paper or string snugly around the base of your finger and mark where it overlaps. Measure that length in millimetres, and that's the circumference. You can also measure the inner diameter of a ring that already fits. Enter either figure here to get your size. Fingers swell a little through the day, so measure in the evening for the truest fit.
- What is the difference between diameter and circumference?
- The diameter is the distance straight across the inside of the ring; the circumference is the distance all the way around the inside. They are linked: circumference equals the diameter times pi (about 3.1416). EU ring sizes are simply the inner circumference in millimetres, which is why they look like larger numbers.
- Are men's and women's ring sizes different?
- The sizing scale is the same for everyone; there is no separate men's or women's system. Men tend to land at larger sizes simply because their fingers are usually bigger. Pick by the actual finger measurement rather than by who the ring is for.
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