Ring size chart and converter
Convert ring sizes between the US, UK, EU and ISO systems, all anchored to the inside diameter and circumference in millimetres. Enter a size you know and read every other system.
Full ring size chart
| US / Canada | UK / Australia | EU / ISO | Japan / China | Diameter (mm) | Circumference (mm) |
|---|---|---|---|---|---|
| 3 | F | 44 | 4 | 14.1 | 44.2 |
| 3.5 | G | 45 | 5 | 14.5 | 45.5 |
| 4 | H | 47 | 7 | 14.9 | 46.8 |
| 4.5 | I | 48 | 8 | 15.3 | 48 |
| 5 | J | 49 | 9 | 15.7 | 49.3 |
| 5.5 | K | 50 | 10 | 16.1 | 50.6 |
| 6 | L | 52 | 12 | 16.5 | 51.9 |
| 6.5 | M | 53 | 13 | 16.9 | 53.1 |
| 7 | N | 54 | 14 | 17.3 | 54.4 |
| 7.5 | O | 56 | 15 | 17.7 | 55.7 |
| 8 | P | 57 | 16 | 18.1 | 57 |
| 8.5 | Q | 58 | 17 | 18.5 | 58.3 |
| 9 | R | 59 | 18 | 19 | 59.5 |
| 9.5 | S | 61 | 19 | 19.4 | 60.8 |
| 10 | T | 62 | 20 | 19.8 | 62.1 |
| 10.5 | U | 63 | 22 | 20.2 | 63.4 |
| 11 | V | 64 | 23 | 20.6 | 64.6 |
| 11.5 | W | 66 | 24 | 21 | 65.9 |
| 12 | X | 67 | 25 | 21.4 | 67.2 |
| 12.5 | Y | 68 | 26 | 21.8 | 68.5 |
| 13 | Z | 69 | 27 | 22.2 | 69.7 |
Average ring sizes: women wear around US 6 to 6.5 (UK L to M, EU 52 to 53), men wear around US 9 to 10.5 (UK R to U, EU 59 to 63). Averages are a starting point only, so measure to be sure.
A ring that fits well should slide over your knuckle with a little resistance and sit snug without leaving a deep mark. The trouble is that the same physical ring is labelled differently in every country. The United States and Canada use a numeric scale that runs in quarter and half steps, the United Kingdom, Ireland and Australia use letters, and most of Europe uses the ISO standard, where the size number is simply the inside circumference of the band in millimetres.
Because all of these labels describe one real dimension, the inside diameter of the band, you can convert between any of them exactly. The chart below is anchored to diameter and circumference in millimetres, so if you know the measurement of a ring that already fits, you can read straight across to a US number, a UK letter or an EU size without guessing.
Ring size questions
What is the most common ring size?
For women the most common sizes are US 6 to 6.5, which is UK L to M or EU 52 to 53. For men the most common are US 9 to 10.5, which is UK R to U or EU 59 to 63. These are averages, so measure to be sure.
How do US and UK ring sizes differ?
US and Canada use numbers in half steps while the UK, Ireland and Australia use letters. A US 7, for example, is a UK N. The bands are the same physical size, only the label differs.
What does the EU ring size number mean?
In the ISO system used across most of Europe the ring size is the inside circumference of the band in millimetres. An EU 54 ring has an inside circumference of about 54 millimetres, which is a US 7.
Should I size up for wide bands?
Yes. A wide band covers more of your finger and feels tighter, so for bands wider than about 6 millimetres many jewelers suggest going up a quarter to a half size.
Where these numbers come from
Every row in this chart is anchored to the inner circumference of the ring in millimetres. The EU/ISO column is that circumference rounded to the nearest whole millimetre, which is why EU 44 sits at 44.2 mm, EU 53 at 53.1 mm and EU 69 at 69.7 mm. The rounding error is never more than half a millimetre and it is not constant across the scale.
- ISO 8653
- Fixes the definition, measurement and designation of ring sizes, expressed as the inner circumference in millimetres. In this chart it gives the EU/ISO column, and through it the diameter and circumference columns.
Reviewed by Jamey Weber, last checked August 5, 2026. Found an error? Report it and it gets fixed in the changelog. See also the full methodology.
Last reviewed and updated on August 5, 2026. Conversion tables are checked against published international sizing standards.