Ring Size Converter
Convert ring sizes between US, UK and EU — or find your size from a measurement in millimetres.
Tip: measure the inside diameter of a ring that fits (straight across), or wrap string around your finger and measure its length for the circumference.
Ring size chart
| US | UK | EU | Diameter (mm) | Circumference (mm) |
|---|---|---|---|---|
| 3 | F | 44 | 14.1 | 44.3 |
| 3.5 | G | 46 | 14.5 | 45.6 |
| 4 | H | 47 | 14.9 | 46.8 |
| 4.5 | I | 48 | 15.3 | 48.1 |
| 5 | J | 49 | 15.7 | 49.3 |
| 5.5 | K | 51 | 16.1 | 50.6 |
| 6 | L | 52 | 16.5 | 51.8 |
| 6.5 | M | 53 | 16.9 | 53.1 |
| 7 | N | 54 | 17.3 | 54.3 |
| 7.5 | O | 56 | 17.7 | 55.6 |
| 8 | P | 57 | 18.1 | 56.9 |
| 8.5 | Q | 58 | 18.5 | 58.1 |
| 9 | R | 59 | 18.9 | 59.4 |
| 9.5 | S | 61 | 19.4 | 60.9 |
| 10 | T | 62 | 19.8 | 62.2 |
| 10.5 | U | 64 | 20.2 | 63.5 |
| 11 | V | 65 | 20.6 | 64.7 |
| 11.5 | W | 66 | 21.0 | 66.0 |
| 12 | X | 67 | 21.4 | 67.2 |
| 12.5 | Y | 69 | 21.8 | 68.5 |
| 13 | Z | 70 | 22.2 | 69.7 |
Convert ring sizes across the US, UK and EU
Ring sizes are not universal: the US and Canada use numbers (3 to 13 with half steps), the UK, Ireland and Australia use letters (A to Z), and most of Europe uses the ISO 8653 system, where the size simply equals the inside circumference of the band in millimetres. This converter links all three to the one measurement that never changes — the physical size of the ring — so you can shop or order from any country with confidence.
Measure the inside diameter or inside circumference of a ring that already fits in millimetres, choose which one you measured, and the tool shows the nearest US number, UK letter and EU size. The full reference chart below lists every size with its inside diameter and circumference so you can read across in either direction.
How to measure your ring size
The most reliable way is to measure a ring you already wear. Lay it flat and measure straight across the inside opening from edge to edge to get the inside diameter, then enter that figure here. Alternatively, wrap a strip of paper or string snugly around the base of your finger, mark where it overlaps, and measure the length in millimetres to get the circumference. Measure at the end of the day when fingers are warm and slightly larger, and aim for a snug fit that still slides over the knuckle.
FAQ
How do I find my ring size in mm? Measure the inside diameter of a ring that fits, straight across from edge to edge, or wrap string around your finger and measure its length for the circumference. Enter either value above and the tool returns the matching size.
What is a US size 7 in UK and EU sizes? A US 7 is roughly a UK N and an EU 54, with an inside diameter of about 17.3 mm and an inside circumference of about 54 mm.
Why is the EU size the same as the circumference? The European ISO 8653 standard defines the ring size as the inside circumference of the band in millimetres, so an EU size of 54 means a circumference of 54 mm.
Are these conversions exact? They are close approximations. Letter and number scales do not line up perfectly between countries, and jewellers round differently, so treat the result as the nearest standard size rather than a guarantee — confirm with a jeweller before buying.