The Real Gem Ring Size Guide
Find Your Perfect Fit
Whether you're treating yourself or surprising someone special, this guide will help you find the right ring size with confidence.
UK and US Ring Sizes
Ring sizes differ between countries, but they all measure the same thing: the circumference of your finger or the inside diameter of the ring. Here's our UK to US conversion chart, with measurements in millimetres.
| UK | US | Circumference (mm) | Diameter (mm) |
|---|---|---|---|
| A | – | 37.8 | 12.0 |
| B | 1 | 39.1 | 12.5 |
| C | 1½ | 40.4 | 12.9 |
| D | 2 | 41.7 | 13.3 |
| E | 2½ | 42.9 | 13.7 |
| F | 3 | 44.2 | 14.1 |
| G | 3¼ | 45.5 | 14.5 |
| H | 4 | 46.8 | 14.9 |
| I | 4½ | 48.0 | 15.3 |
| J | 4¾ | 48.7 | 15.5 |
| K | 5¼ | 50.0 | 15.9 |
| L | 5¾ | 51.2 | 16.3 |
| M | 6¼ | 52.5 | 16.7 |
| N | 6¾ | 53.8 | 17.1 |
| O | 7¼ | 55.1 | 17.5 |
| P | 7¾ | 56.3 | 17.9 |
| Q | 8¼ | 57.6 | 18.3 |
| R | 8¾ | 58.9 | 18.7 |
| S | 9¼ | 60.2 | 19.1 |
| T | 9¾ | 61.4 | 19.5 |
| U | 10¼ | 62.7 | 19.9 |
| V | 10¾ | 64.0 | 20.3 |
| W | 11¼ | 65.3 | 20.7 |
| X | 11¾ | 66.6 | 21.1 |
| Y | 12¼ | 67.8 | 21.5 |
| Z | 12¾ | 68.5 | 21.8 |
| Z+1 | 13½ | 70.2 | 22.4 |
| Z+2 | 14¼ | 71.4 | 22.8 |
How to Measure
Option 1: use a ring you already own
- Measure the inside diameter of the ring in millimetres.
- Find that number in the diameter column above.
Option 2: use a strip of paper or string
- Wrap it around the base of your finger.
- Mark where the ends meet and measure the length in millimetres.
- Find that number in the circumference column above.
The Real Gem tip: measure at the end of the day, when your fingers are at their largest. Avoid measuring when your hands are cold, as you'll get a smaller reading.
Sizing Tips
- Rings with wider bands can feel tighter; consider going up half a size.
- Fingers on your dominant hand tend to be slightly larger.
- Engagement rings are traditionally worn on the left ring finger.
- If you're between sizes, it's usually safer to size up.
- Most rings can be resized (except full eternity bands and some bespoke designs), so don't worry if it isn't perfect first time.
Still Unsure?
Just tell us when you order and we'll confirm the fit with you before dispatch. Or contact us and we'll help you work it out.