Ring size converter
Pick a system, type a size and read it in every other system, with the difference in millimetres.
US and Canada 7 is 54 in ISO and 7 in US sizes, with an inside diameter of 17.3 mm.
| System | Size | Match |
|---|---|---|
| US and Canada | 7 | exact |
| UK and Australia | N½ | exact |
| ISO / Europe | 54 | closest: −0.4 mm |
| Switzerland, Italy, Spain | 14 | closest: −0.4 mm |
| Japan | 14 | exact |
| Hong Kong and China | 15 | exact |
| India | 14 | closest: −0.4 mm |
How the converter works
Every size is turned into an inside circumference in millimetres, the unit of ISO 8653, then looked up in the other systems. Each system has sizes at fixed steps, so the result is the nearest size, and the difference is shown instead of hidden.
When the difference is under 0.15 mm the size is shown as exact. Otherwise it says closest, with the gap in millimetres: a minus sign means the ring will be a little smaller than the size you typed.
Questions
Why is the converted size not exact?
Each system has sizes at its own steps, so a size in one system usually falls between two in another. The converter shows the closest one and the gap in millimetres.
Which size should I choose between two?
If you are between sizes, the larger one is the safer choice for a ring that must pass the knuckle, and a jeweller can often adjust a ring that is slightly loose. Check this with the shop you buy from.