All the methods you need to accurately measure ring sizes, plus full international conversion tables.
Understanding ring sizes and how to measure for them is essential before any ring purchase. This page covers every measurement method, what the numbers mean, and how to convert between the world's major ring sizing systems.
Ring sizes are standardised measurements of a ring's inner circumference or diameter. The number or letter you're given by a jeweller corresponds to a specific inner measurement. Different countries use completely different scales — which is why online shopping internationally often causes confusion.
| System | Type | Used In | Example |
|---|---|---|---|
| US/Canada | Numbers (3–14+) | USA, Canada | Size 7 = 17.3mm |
| UK/IRE/AUS | Letters (A–Z+) | UK, Ireland, Australia | Size N = 17.3mm |
| EU/French | mm circumference | Europe | Size 54 = 17.3mm |
| Japanese | Numbers (1–30+) | Japan, China | Size 14 = 17.3mm |
| Swiss | Diameter − 40 | Switzerland | Size 14 = 17.3mm |
Make sure it passes over your knuckle comfortably.
Use a pen to mark the exact point where the paper meets itself.
Measure from the start of the paper to your mark. This is your circumference in mm.
Use the chart on our ring size chart page or our calculator.
Measure the inside diameter of a ring that fits the correct finger. Measure in mm and use the diameter column on our ring dimensions page.
| US | UK | EU | Japan | Swiss | Diameter (mm) | Circumference (mm) |
|---|---|---|---|---|---|---|
| 3 | F | 44 | 4 | 4 | 14.1 | 44.2 |
| 3.5 | G | 45 | 5 | 5 | 14.5 | 45.6 |
| 4 | H | 46.5 | 7 | 6.5 | 14.9 | 46.8 |
| 4.5 | I | 48 | 8 | 8 | 15.3 | 48.0 |
| 5 | J | 49 | 9 | 9 | 15.7 | 49.3 |
| 5.5 | K | 50.5 | 11 | 10.5 | 16.1 | 50.6 |
| 6 | L | 51.5 | 12 | 11.5 | 16.5 | 51.9 |
| 6.5 | M | 53 | 13 | 13 | 16.9 | 53.2 |
| 7 | N | 54 | 14 | 14 | 17.3 | 54.4 |
| 7.5 | O | 55.5 | 16 | 15.5 | 17.7 | 55.7 |
| 8 | P | 57 | 17 | 17 | 18.2 | 57.2 |
| 8.5 | Q | 58 | 18 | 18 | 18.5 | 58.2 |
| 9 | R | 59 | 19 | 19 | 18.9 | 59.3 |
| 9.5 | S | 61 | 21 | 21 | 19.4 | 61.0 |
| 10 | T | 62 | 22 | 22 | 19.8 | 62.2 |
| 10.5 | U | 63.5 | 24 | 23.5 | 20.2 | 63.5 |
| 11 | V | 65 | 25 | 25 | 20.7 | 65.0 |
| 11.5 | W | 66 | 26 | 26 | 21.1 | 66.2 |
| 12 | X | 67.5 | 28 | 27.5 | 21.5 | 67.5 |
| 12.5 | Y | 68.5 | 29 | 28.5 | 21.9 | 68.8 |
| 13 | Z | 70 | 30 | 30 | 22.3 | 70.1 |
| 14 | Z+2 | 71 | 31 | 31 | 22.7 | 71.3 |