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International ring size converter
Convert any ring size between US, UK, EU/ISO, Japan and Switzerland — with the exact diameter and circumference in millimetres. Verified against ISO 8653.
Your size is US 7 (UK N½, EU 54).
Fit confidence Exact table match
Measurement confidence 70/100 · Medium Standard chart conversion; final fit still depends on band width and knuckle shape. Confirm with a printable or physical sizer before ordering an expensive ring.
- US
- 7
- UK
- N½
- EU / ISO
- 54
- Japan
- 14
- CH / IT / ES
- 14
- Ø mm
- 17.32
- Circ mm
- 54.4
| US | UK | EU | JP | CH | Ø mm | Circ mm |
|---|---|---|---|---|---|---|
| 3 | F½ | 44 | 4 | 4 | 14.07 | 44.2 |
| 3.5 | G½ | 45 | 5 | 5 | 14.48 | 45.5 |
| 4 | H½ | 47 | 7 | 7 | 14.88 | 46.8 |
| 4.5 | I½ | 48 | 8 | 8 | 15.29 | 48.0 |
| 5 | J½ | 49 | 9 | 9 | 15.70 | 49.3 |
| 5.5 | K½ | 51 | 10 | 11 | 16.10 | 50.6 |
| 6 | L½ | 52 | 12 | 12 | 16.51 | 51.9 |
| 6.5 | M½ | 53 | 13 | 13 | 16.92 | 53.1 |
| 7 | N½ | 54 | 14 | 14 | 17.32 | 54.4 |
| 7.5 | O½ | 56 | 15 | 16 | 17.73 | 55.7 |
| 8 | P½ | 57 | 16 | 17 | 18.14 | 57.0 |
| 8.5 | Q½ | 58 | 17 | 18 | 18.54 | 58.3 |
| 9 | R½ | 60 | 18 | 20 | 18.95 | 59.5 |
| 9.5 | S½ | 61 | 19 | 21 | 19.35 | 60.8 |
| 10 | T½ | 62 | 20 | 22 | 19.76 | 62.1 |
| 10.5 | U½ | 63 | 22 | 23 | 20.17 | 63.4 |
| 11 | V½ | 65 | 23 | 25 | 20.57 | 64.6 |
| 11.5 | W½ | 66 | 24 | 26 | 20.98 | 65.9 |
| 12 | Y | 67 | 25 | 27 | 21.39 | 67.2 |
| 12.5 | Z | 68 | 26 | 28 | 21.79 | 68.5 |
| 13 | Z½ | 70 | 27 | 30 | 22.20 | 69.7 |
Ring size measurement wizard
Choose what you have: a ring, a finger measurement, a smart-ring order, or a surprise. The wizard points you to the safest method.
Use the on-screen sizer or printable circles to match the inside edge of the ring.
Use the on-screen sizer or printable circles to match the inside edge of the ring.
How the conversion works
Every value comes from one rule: the US size sets the inner diameter (0.458 + 0.032 × US, in inches), the circumference is π × the diameter, EU/ISO is that circumference in millimetres, and UK letters and Japanese numbers come from a verified lookup table.
See the full ring size chart →
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Frequently asked questions
How do I measure my ring size at home?
The most reliable way is to measure the inner diameter of a ring that already fits, in millimetres, and match it on the chart. If you have no ring, wrap a thin strip of paper around the base of your finger, mark where it overlaps, and measure the length in mm — that is the circumference. Measure at the end of the day when fingers are largest.
Why does the string method give the wrong size?
String and thread stretch and compress the skin, and slide over the knuckle too easily, so they typically read half a size to a full size too large. Use a stiff paper strip or, better, the inner diameter of an existing ring.
I am between sizes — should I size up or down?
Size up. A slightly loose ring is wearable and can be padded; a ring that is too tight may not pass the knuckle at all. This is especially true for wide bands, which fit tighter.
Are international ring size conversions exact?
US, EU/ISO and millimetre values convert cleanly. UK letters, Japan and India are lookup-based and can differ by up to a full size between charts. When a retailer accepts a millimetre measurement, order by diameter or circumference rather than a converted local size.