Free interactive calculator, international conversion charts, and step-by-step measuring guides — everything in one place.
Quick Access
Enter your mm measurement and instantly convert to US, UK, EU, Japanese and Swiss sizes.
Open Calculator →Complete international ring size conversion table — US, UK, EU, Japan, Swiss, diameter and circumference.
View Chart →Step-by-step guides for measuring your ring size at home using paper, string, or an existing ring.
Read Guide →Print calibrated ring circles at actual size and match against your existing rings for an instant size.
Print Sizer →All Pages
Browse every guide on SizeRings.com — organised by topic.
Interactive Tool
For wide bands (6mm+) order half a size up. If between sizes, always choose the larger. Full calculator →
Enter your measurement above and click Find My Ring Size
Size Reference
The most common sizes at a glance. View the complete chart with all 22 sizes →
| US / Canada | UK / IRE / AUS | EU / French | Japan | Diameter (mm) | Circumference (mm) |
|---|---|---|---|---|---|
| 5 | J | 49 | 9 | 15.7 | 49.3 |
| 5.5 | K | 50.5 | 11 | 16.1 | 50.6 |
| 6 | L | 51.5 | 12 | 16.5 | 51.9 |
| 6.5 | M | 53 | 13 | 16.9 | 53.2 |
| 7 | N | 54 | 14 | 17.3 | 54.4 |
| 7.5 | O | 55.5 | 16 | 17.7 | 55.7 |
| 8 | P | 57 | 17 | 18.2 | 57.2 |
| 8.5 | Q | 58 | 18 | 18.5 | 58.2 |
| 9 | R | 59 | 19 | 18.9 | 59.3 |
| 9.5 | S | 61 | 21 | 19.4 | 61.0 |
| 10 | T | 62 | 22 | 19.8 | 62.2 |
| 10.5 | U | 63.5 | 24 | 20.2 | 63.5 |
| 11 | V | 65 | 25 | 20.7 | 65.0 |
| 12 | X | 67.5 | 28 | 21.5 | 67.5 |
Includes Swiss sizes, half sizes, and all 22 rows on the full chart page.
Expert Advice
Fingers are at their largest at the end of the day due to normal swelling. Measuring in the morning can give a reading up to half a size smaller.
Cold shrinks fingers; heat expands them. Always measure at comfortable room temperature for the most consistent result.
For bands 6mm or wider, go at least half a size up. Wider bands contact more of the finger and feel significantly tighter.
If between two sizes, choose the larger. A slightly loose ring is easily fixed with a ring guard or jeweller visit. Too tight is far harder to fix.
The ring must pass over your knuckle. If your knuckle is noticeably larger than the base, measure both and size for a comfortable knuckle fit.
For engagement rings and wedding bands, always get professionally sized. It's free, takes 2 minutes, and removes all guesswork.
Common Questions
More questions answered across our how-to guides and size chart pages.