Ring Size in mm — Diameter & Circumference Tables
Millimetres are the one unit every sizing system shares. Look up any diameter or circumference here, with the US, UK, EU, Japanese and Indian sizes for each.
Last updated: November 2026
Look up by diameter (across a ring)
| Inner diameter | US size | UK | EU | Circumference |
|---|---|---|---|---|
| 14.1 mm | US 3 | F | 44 | 44.2 mm |
| 14.5 mm | US 3.5 | G | 46 | 45.5 mm |
| 14.9 mm | US 4 | H½ | 47 | 46.8 mm |
| 15.3 mm | US 4.5 | I½ | 48 | 48.0 mm |
| 15.7 mm | US 5 | J½ | 49 | 49.3 mm |
| 16.1 mm | US 5.5 | K½ | 51 | 50.6 mm |
| 16.5 mm | US 6 | L½ | 52 | 51.9 mm |
| 16.9 mm | US 6.5 | M½ | 53 | 53.1 mm |
| 17.3 mm | US 7 | N½ | 54 | 54.4 mm |
| 17.7 mm | US 7.5 | O½ | 56 | 55.7 mm |
| 18.1 mm | US 8 | P½ | 57 | 57.0 mm |
| 18.5 mm | US 8.5 | Q½ | 58 | 58.3 mm |
| 18.9 mm | US 9 | R½ | 60 | 59.5 mm |
| 19.4 mm | US 9.5 | S½ | 61 | 60.9 mm |
| 19.8 mm | US 10 | T½ | 62 | 62.1 mm |
| 20.2 mm | US 10.5 | U½ | 63 | 63.4 mm |
| 20.6 mm | US 11 | V½ | 65 | 64.6 mm |
| 21.0 mm | US 11.5 | W½ | 66 | 66.0 mm |
| 21.4 mm | US 12 | X½ | 67 | 67.2 mm |
| 21.8 mm | US 12.5 | Y½ | 69 | 68.5 mm |
| 22.2 mm | US 13 | Z½ | 70 | 69.7 mm |
Look up by circumference (around a finger)
| Circumference | US size | UK | EU | Diameter |
|---|---|---|---|---|
| 44.2 mm | US 3 | F | 44 | 14.1 mm |
| 45.5 mm | US 3.5 | G | 46 | 14.5 mm |
| 46.8 mm | US 4 | H½ | 47 | 14.9 mm |
| 48.0 mm | US 4.5 | I½ | 48 | 15.3 mm |
| 49.3 mm | US 5 | J½ | 49 | 15.7 mm |
| 50.6 mm | US 5.5 | K½ | 51 | 16.1 mm |
| 51.9 mm | US 6 | L½ | 52 | 16.5 mm |
| 53.1 mm | US 6.5 | M½ | 53 | 16.9 mm |
| 54.4 mm | US 7 | N½ | 54 | 17.3 mm |
| 55.7 mm | US 7.5 | O½ | 56 | 17.7 mm |
| 57.0 mm | US 8 | P½ | 57 | 18.1 mm |
| 58.3 mm | US 8.5 | Q½ | 58 | 18.5 mm |
| 59.5 mm | US 9 | R½ | 60 | 18.9 mm |
| 60.9 mm | US 9.5 | S½ | 61 | 19.4 mm |
| 62.1 mm | US 10 | T½ | 62 | 19.8 mm |
| 63.4 mm | US 10.5 | U½ | 63 | 20.2 mm |
| 64.6 mm | US 11 | V½ | 65 | 20.6 mm |
| 66.0 mm | US 11.5 | W½ | 66 | 21.0 mm |
| 67.2 mm | US 12 | X½ | 67 | 21.4 mm |
| 68.5 mm | US 12.5 | Y½ | 69 | 21.8 mm |
| 69.7 mm | US 13 | Z½ | 70 | 22.2 mm |
Honest note on charts: Ring size charts vary by up to half a size between jewellers. Always confirm your size in millimetres — inner diameter or circumference — with the jeweller you are buying from before you order.
Measured something in between? The calculator interpolates and shows the precise US estimate. Full chart: ring size chart. Measuring help: how to measure ring size.
Common questions — what size is…?
What ring size is 17mm?
On the standard chart, 17mm corresponds to US 7 — diameter 17.3 mm, circumference 54.4 mm, UK N½, EU 54, Japan/India 14.
What ring size is 17.3mm?
On the standard chart, 17.3mm corresponds to US 7 — diameter 17.3 mm, circumference 54.4 mm, UK N½, EU 54, Japan/India 14.
What ring size is 54mm?
On the standard chart, 54mm corresponds to US 7 — diameter 17.3 mm, circumference 54.4 mm, UK N½, EU 54, Japan/India 14.
What ring size is 16.5mm?
On the standard chart, 16.5mm corresponds to US 6 — diameter 16.5 mm, circumference 51.9 mm, UK L½, EU 52, Japan/India 12.
What ring size is 52mm?
On the standard chart, 52mm corresponds to US 6 — diameter 16.5 mm, circumference 51.9 mm, UK L½, EU 52, Japan/India 12.
What ring size is 19.8mm?
On the standard chart, 19.8mm corresponds to US 10 — diameter 19.8 mm, circumference 62.1 mm, UK T½, EU 62, Japan/India 21.
What ring size is 62mm?
On the standard chart, 62mm corresponds to US 10 — diameter 19.8 mm, circumference 62.1 mm, UK T½, EU 62, Japan/India 21.
What ring size is 18.1mm?
On the standard chart, 18.1mm corresponds to US 8 — diameter 18.1 mm, circumference 57.0 mm, UK P½, EU 57, Japan/India 16.