Free tool
Ring Size Calculator
Enter a diameter or circumference — get your size in US, UK, EU, and JP.
Inside diameter of an existing ring, measured in mm.
Enter a measurement above to see your ring size.
Tip: Measuring an existing ring is more reliable than paper or string. When in doubt, size up.
Guide
How to Measure Your Ring Size at Home
Method 1: Measure an existing ring
- Place a well-fitting ring flat on a ruler.
- Measure the inside diameter in mm.
- Enter that number above using Diameter mode.
Method 2: Measure your finger
- Wrap a thin strip of paper around the base of your finger.
- Mark the overlap, then measure that length in mm.
- Enter it above using Circumference mode.
Method 1 is more reliable. Measure at the end of the day when fingers are at their largest.
Reference
Ring Size Chart — US, UK, EU & JP
US sizes 3–13 with half sizes. All measurements in mm.
| US Size | UK Size | EU Size | JP Size | Diameter (mm) | Circumference (mm) |
|---|---|---|---|---|---|
| 3 | F | 44 | 4 | 14.05 | 44.1 |
| 3½ | G | 45 | 5 | 14.45 | 45.4 |
| 4 | H | 47 | 7 | 14.86 | 46.7 |
| 4½ | I | 48 | 8 | 15.27 | 48 |
| 5 | J½ | 49 | 9 | 15.68 | 49.3 |
| 5½ | K½ | 51 | 10 | 16.1 | 50.6 |
| 6 | L½ | 52 | 12 | 16.51 | 51.9 |
| 6½ | M½ | 53 | 13 | 16.92 | 53.1 |
| 7 | N½ | 55 | 14 | 17.35 | 54.5 |
| 7½ | O | 56 | 15 | 17.75 | 55.7 |
| 8 | P | 57 | 16 | 18.19 | 57.2 |
| 8½ | Q | 59 | 17 | 18.61 | 58.5 |
| 9 | R | 60 | 18 | 19.02 | 59.7 |
| 9½ | R½ | 61 | 19 | 19.43 | 61 |
| 10 | S½ | 62 | 20 | 19.84 | 62.3 |
| 10½ | T½ | 64 | 21 | 20.27 | 63.7 |
| 11 | U½ | 65 | 22 | 20.68 | 65 |
| 11½ | V | 66 | 23 | 21.08 | 66.2 |
| 12 | W | 68 | 24 | 21.49 | 67.5 |
| 12½ | X | 69 | 25 | 21.89 | 68.8 |
| 13 | Z | 70 | 26 | 22.33 | 70.1 |
EU: ISO 8653. JP: JIS B7527.
Conversion
International Ring Size Conversion
US and JP use numbers. UK uses letters. EU sizes equal finger circumference in mm.
| System | Scale | Range | Example |
|---|---|---|---|
| US / Canada | Numeric | 3 – 13 | 7 |
| UK / AU / IE / NZ | Alphabetic | F – Z | N½ |
| EU (ISO 8653) | Circumference in mm | 44 – 70 | 55 |
| Japan / China | Numeric (JIS) | 4 – 26 | 14 |
Use the chart above or enter your measurement in the calculator to convert.
FAQ
Common Questions
- What's the most accurate way to find my ring size?
- Measure the inside diameter of a ring that already fits. Paper and string can stretch, so they're less reliable.
- What if I'm between two sizes?
- Size up. A slightly large ring is easier to resize than one that's too tight.
- How do I convert US ring size to EU or UK?
- Find your US size in the chart above and read across. US 6 = EU 52 = UK L½. US 7 = EU 55 = UK N½. US 8 = EU 57 = UK P.
- What is US size 7 in other systems?
- US 7 = EU 55 = UK N½ = JP 14. Inside diameter: 17.35 mm.
- Does finger size change during the day?
- Yes. Fingers are largest in the afternoon. Measure then for the best fit.