How to Use This Guide
- 1 Measure the inside diameter of a ring you already own (in millimeters).
- 2 Find that diameter in the first column of the chart below.
- 3 Match it with your country's sizing system (US, UK, EU, JP, etc.).
Ring Size Conversion Chart
Below is a sample of the conversion table. The full chart in the app covers every quarter size for more accuracy.
| Diameter (mm) | US / CA / MX | UK / AU / NZ | China | Japan | S. Korea | India | Italy | Spain | Netherlands | Switzerland | EU |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 11.63 | 0 | – | – | – | – | – | -3.5 | -3.5 | -3.5 | -3.5 | 36.5 |
| 12.04 | 1/2 | A | – | – | – | – | -2.2 | -2.2 | -2.2 | -2.2 | 37.8 |
| 12.45 | 1 | B | 1 | 1 | 1 | – | -0.9 | -0.9 | -0.9 | -0.9 | 39.1 |
| 13.26 | 2 | D | 2 | 2 | 2 | 2 | 1.7 | 1.7 | 1.7 | 1.7 | 41.7 |
| 14.07 | 3 | F | 4 | 4 | 4 | – | 4.2 | 4.2 | 4.2 | 4.2 | 44 |
| 15.29 | 4 1/2 | I | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 48 |
| 16.51 | 6 | L 1/2 | 11 | 11 | 11 | 12 | 11.9 | 11.9 | 11.9 | 11.9 | 51.9 |
| 17.32 | 7 | N 1/2 | 14 | 14 | 14 | 14 | 14.4 | 14.4 | 14.4 | 14.4 | 54 |
| 18.14 | 8 | P 1/2 | 16 | 16 | 16 | 17 | 17 | 17 | 17 | 17 | 57 |
| 19.35 | 9 1/2 | S 1/2 | 19 | 19 | 19 | 21 | 20.8 | 20.8 | 20.8 | 20.8 | 61 |
| 20.57 | 11 | V 1/2 | 23 | 23 | 23 | 25 | 24.6 | 24.6 | 24.6 | 24.6 | 64.6 |
| 22.00 | 12 3/4 | Z | 29 | 29 | 29 | 29 | 29.1 | 29.1 | 29.1 | 29.1 | 69 |
| 23.22 | 14 1/4 | Z3 | – | – | – | 33 | 32.9 | 32.9 | 32.9 | 32.9 | 73 |
| 24.64 | 16 | – | – | – | – | 37 | 37.4 | 37.4 | 37.4 | 37.4 | 77.4 |
The full chart inside the app covers every quarter size for even more accuracy.
Tips for Measuring Ring Size
Measure in the evening
Fingers are slightly larger at night due to normal daily swelling.
Avoid the cold
Low temperatures shrink your fingers and give inaccurate readings.
Measure multiple times
Repeat measurements on different days to reduce error.
Dominant-hand differences
Your writing hand can be up to half a size larger than the other.
Why Use the Ring Sizer App?
On-screen measurement — Place your ring on the screen to find the exact size instantly.
Multi-country conversion — Instantly switch between US, UK, EU, JP, and other systems.
Save your profile — Save your size for future purchases so you never forget.
Final Thoughts
A ring should feel comfortable, secure, and easy to wear every day. With this guide and our app, you can confidently order the perfect fit — no matter where in the world your jeweler is.
