Approximate reference · Check the brand’s current chart
Ring size reference
A complete cross-reference of ring sizes between the US, UK, EU and Japanese systems — with inner diameter and circumference in millimetres so you can size a ring you already own.
| US | UK | EU | JP | Ø (mm) | Circ. (mm) |
|---|---|---|---|---|---|
| 4 | H | 47 | 7 | 14.9 | 46.8 |
| 4.5 | I | 48 | 8 | 15.3 | 48.0 |
| 5 | J 1/2 | 49 | 9 | 15.7 | 49.3 |
| 5.5 | K 1/2 | 50 | 10 | 16.1 | 50.6 |
| 6 | L 1/2 | 51.5 | 11 | 16.5 | 51.8 |
| 6.5 | M 1/2 | 53 | 12 | 16.9 | 53.1 |
| 7 | N 1/2 | 54 | 13 | 17.3 | 54.4 |
| 7.5 | O 1/2 | 55.5 | 14 | 17.7 | 55.7 |
| 8 | P 1/2 | 57 | 16 | 18.2 | 57.0 |
| 8.5 | Q 1/2 | 58 | 17 | 18.6 | 58.3 |
| 9 | R 1/2 | 59 | 18 | 19.0 | 59.5 |
| 9.5 | S 1/2 | 61 | 19 | 19.4 | 60.8 |
| 10 | T 1/2 | 62 | 20 | 19.8 | 62.1 |
| 10.5 | U 1/2 | 63 | 22 | 20.2 | 63.4 |
| 11 | V 1/2 | 64.5 | 23 | 20.6 | 64.6 |
| 12 | X 1/2 | 67 | 25 | 21.4 | 67.2 |
| 13 | Z 1/2 | 69 | 27 | 22.2 | 69.7 |
Measure an existing ring
Place a ring you already wear on a ruler and measure the inner diameter in millimetres. Look up the diameter column to find your size in every system.
Measure your finger
Wrap a strip of paper around the base of your finger, mark where it overlaps, and measure that length in millimetres — that's your circumference.
Measure in normal conditions
Finger size can change with temperature and activity. Measure at a comfortable room temperature and confirm with a jeweler’s ring sizer, especially for wide bands or valuable purchases.
Knuckle versus base
If your knuckle is significantly larger than your finger base, size up. Most jewellers recommend a fit that slides over the knuckle with mild resistance.
Common questions
- Are UK and US ring sizes the same?
- No. UK uses letters (H, J 1/2, etc.) while the US uses half-step numerics. A US 6 is roughly a UK L 1/2.
- Is the EU number my circumference?
- Yes — EU ring sizes correspond closely to the inner circumference of the band in millimetres. EU 54 ≈ 54 mm inner circumference.