Free tool
Ring size converter
Convert in any direction between UK, US, European, Japanese and Swiss. If you are starting from a ring rather than a size, the size finder measures it first.
The full conversion chart
European sizing is the circumference in millimetres. Japanese sizes run 1 to 27 on their own scale. Swiss sizes are the European circumference less 40.
| UK | US | EU | JP | Swiss | Circumference | Diameter |
|---|---|---|---|---|---|---|
| A | 0.5 | 38 | 1 | -2 | 37.8 mm | 12.03 mm |
| B | 1 | 39 | 1 | -1 | 39.1 mm | 12.45 mm |
| C | 1.5 | 40.5 | 1 | 0.5 | 40.4 mm | 12.86 mm |
| D | 2 | 41.5 | 2 | 1.5 | 41.7 mm | 13.27 mm |
| E | 2.5 | 43 | 3 | 3 | 42.9 mm | 13.66 mm |
| F | 3 | 44 | 5 | 4 | 44.2 mm | 14.07 mm |
| G | 3.5 | 45.5 | 6 | 5.5 | 45.5 mm | 14.48 mm |
| H | 4 | 47 | 7 | 7 | 46.8 mm | 14.90 mm |
| I | 4.5 | 48 | 8 | 8 | 48.0 mm | 15.28 mm |
| J | 5 | 48.5 | 9 | 8.5 | 48.7 mm | 15.50 mm |
| K | 5.5 | 50 | 10 | 10 | 50.0 mm | 15.92 mm |
| L | 6 | 51 | 11 | 11 | 51.2 mm | 16.30 mm |
| M | 6.5 | 52.5 | 13 | 12.5 | 52.5 mm | 16.71 mm |
| N | 7 | 54 | 14 | 14 | 53.8 mm | 17.13 mm |
| O | 7.5 | 55 | 15 | 15 | 55.1 mm | 17.54 mm |
| P | 8 | 56.5 | 16 | 16.5 | 56.3 mm | 17.92 mm |
| Q | 8.5 | 57.5 | 18 | 17.5 | 57.6 mm | 18.33 mm |
| R | 9 | 59 | 19 | 19 | 58.9 mm | 18.75 mm |
| S | 9.5 | 60 | 20 | 20 | 60.2 mm | 19.16 mm |
| T | 10 | 61.5 | 21 | 21.5 | 61.4 mm | 19.54 mm |
| U | 10.5 | 62.5 | 23 | 22.5 | 62.7 mm | 19.96 mm |
| V | 11 | 64 | 24 | 24 | 64.0 mm | 20.37 mm |
| W | 11.5 | 65.5 | 25 | 25.5 | 65.3 mm | 20.79 mm |
| X | 12 | 66.5 | 27 | 26.5 | 66.6 mm | 21.20 mm |
| Y | 12.5 | 68 | 28 | 28 | 67.8 mm | 21.58 mm |
| Z | 13 | 69 | 29 | 29 | 69.1 mm | 22.00 mm |
Conversion questions
- What is a UK size N in US sizes?
- A UK N is a US 7. The UK uses letters on the Wheatsheaf scale and the US uses numbers, and they do not line up neatly: roughly two UK letters to one US size, which is why converting by eye goes wrong.
- How do European ring sizes work?
- European sizing under ISO 8653 is simply the inner circumference of the ring in millimetres. A EU 54 has a 54mm circumference. It is the most sensible system of the three because it measures the actual thing.
- Are UK and Australian ring sizes the same?
- Yes. Australia, New Zealand, Ireland and South Africa all use the same A to Z letter scale as the UK, so a UK N is an Australian N.
- Why do different shops give me different sizes?
- Because they measure differently. A plastic gauge, a steel mandrel and a paper strip will all disagree by up to half a size, and a wide band fits tighter than a narrow one at the same nominal size. Measure with the width you intend to buy.
- Can I convert a ring size from a diameter measurement?
- Yes, and it is the most reliable home method. Multiply the inner diameter in millimetres by pi to get the circumference, then read it off the chart. A 17.3mm diameter is 54.3mm around, which is a UK N.