Ring Size Conversion Chart: UK vs US Sizes
Shopping for a ring from the US, or converting a size you were given abroad? The UK and the US use two completely different ring size systems: the UK scale runs in letters from A to Z, while the US scale runs in numbers. There is no formula between the two, but both are simply labels for the inside circumference of the ring in millimetres, so converting is just a matter of looking it up.
UK vs US ring size conversion chart
All measurements are the inside of the ring, in millimetres. Australia, Ireland, New Zealand and South Africa use the same letters as the UK; Canada uses the US numbers.
| UK size | US size | Inside circumference (mm) | Inside diameter (mm) |
|---|---|---|---|
| F | 3 | 44.2 | 14.1 |
| G | 3.5 | 45.5 | 14.5 |
| H | 4 | 46.8 | 14.9 |
| I | 4.5 | 48.0 | 15.3 |
| J½ | 5 | 49.3 | 15.7 |
| K½ | 5.5 | 50.6 | 16.1 |
| L½ | 6 | 51.9 | 16.5 |
| M½ | 6.5 | 53.1 | 16.9 |
| N½ | 7 | 54.4 | 17.3 |
| O½ | 7.5 | 55.7 | 17.7 |
| P½ | 8 | 57.0 | 18.1 |
| Q½ | 8.5 | 58.2 | 18.5 |
| R½ | 9 | 59.5 | 18.9 |
| S½ | 9.5 | 60.8 | 19.4 |
| T½ | 10 | 62.1 | 19.8 |
| U½ | 10.5 | 63.4 | 20.2 |
| V½ | 11 | 64.6 | 20.6 |
| W½ | 11.5 | 65.9 | 21.0 |
| X½ | 12 | 67.2 | 21.4 |
| Y½ | 12.5 | 68.5 | 21.8 |
| Z½ | 13 | 69.7 | 22.2 |
How to find your ring size at home
Measure a ring you already own. Take a ring that fits the finger you are shopping for and measure its inside diameter in millimetres with a ruler. Match that measurement to the chart above to find your UK letter and US number.
Measure your finger. Wrap a thin strip of paper or a piece of string around the base of your finger, mark where it overlaps, and measure the length in millimetres. That figure is your inside circumference - match it to the chart above.
Tips for the right fit
- Measure at the end of the day, when your fingers are warm. Finger size changes slightly through the day and with the weather.
- Wider bands feel tighter, so if you are choosing a wide band, consider going up half a size.
- If you fall between two sizes, choose the larger one. A ring that is slightly loose can usually be sized down, while one that is too small cannot be worn at all.
- Published charts vary slightly between jewellers, so when precision matters, quote your inside circumference in millimetres rather than the letter or number.
Still unsure?
Pop into our Hatton Garden showroom at Suite 19, 88-90 Hatton Garden, London EC1N 8PN and we will measure your finger for you, or book an appointment and we can talk through sizing for the ring you have in mind.
Written by Mayru Mehta
