Ring size chart
The full conversion table from US size 3 to 13, with UK/Australia letters, EU/ISO numbers, Japanese (JIS) sizes and the exact measurements in both millimetres and inches. Scroll the table sideways on mobile, the page itself stays put.
| USUS / Canada | UKUK / AU | EUEU / ISO | JPJapan | mmCircumference | inCircumference | mmDiameter | inDiameter |
|---|---|---|---|---|---|---|---|
| 3 | F½ | 44 | 4 | 44.2 | 1.74 | 14.1 | 0.555 |
| 3½ | G½ | 45 | 5 | 45.4 | 1.79 | 14.5 | 0.571 |
| 4 | H½ | 47 | 7 | 46.7 | 1.84 | 14.9 | 0.587 |
| 4½ | I½ | 48 | 8 | 48.0 | 1.89 | 15.3 | 0.602 |
| 5 | J½ | 49 | 9 | 49.3 | 1.94 | 15.7 | 0.618 |
| 5½ | K½ | 51 | 10 | 50.5 | 1.99 | 16.1 | 0.634 |
| 6 | L½ | 52 | 11 | 51.8 | 2.04 | 16.5 | 0.650 |
| 6½ | M½ | 53 | 13 | 53.1 | 2.09 | 16.9 | 0.665 |
| 7 | N½ | 54 | 14 | 54.4 | 2.14 | 17.3 | 0.681 |
| 7½ | O½ | 56 | 15 | 55.6 | 2.19 | 17.7 | 0.697 |
| 8 | P½ | 57 | 16 | 56.9 | 2.24 | 18.1 | 0.713 |
| 8½ | Q½ | 58 | 18 | 58.2 | 2.29 | 18.5 | 0.728 |
| 9 | R½ | 59 | 19 | 59.5 | 2.34 | 18.9 | 0.744 |
| 9½ | S½ | 61 | 20 | 60.7 | 2.39 | 19.3 | 0.760 |
| 10 | T½ | 62 | 21 | 62.0 | 2.44 | 19.7 | 0.776 |
| 10½ | U½ | 63 | 22 | 63.3 | 2.49 | 20.1 | 0.791 |
| 11 | V½ | 65 | 24 | 64.6 | 2.54 | 20.5 | 0.807 |
| 11½ | W½ | 66 | 25 | 65.8 | 2.59 | 21.0 | 0.827 |
| 12 | X½ | 67 | 26 | 67.1 | 2.64 | 21.4 | 0.843 |
| 12½ | Y½ | 68 | 27 | 68.4 | 2.69 | 21.8 | 0.858 |
| 13 | Z½ | 70 | 29 | 69.7 | 2.74 | 22.2 | 0.874 |
How to read the chart
Every row describes one physical ring, shown several ways. Find the size you already know in its column, then read across for the equivalents. If you only have a millimetre or inch measurement, match it to the circumference or diameter columns.
The four main sizing systems
- US & Canada, numeric, with half sizes. Each whole size adds 0.8 mm of diameter (about 2.55 mm of circumference).
- UK, Ireland, Australia & New Zealand, letters A to Z, with ½ steps. One letter is roughly 1.25 mm of circumference.
- EU / ISO 8653, the size number equals the inner circumference in millimetres, so an EU 54 measures 54 mm around.
- Japan (JIS), also China & Korea, numeric, based on the inner diameter in roughly ⅓ mm steps.
Why ring size charts disagree
If you compare charts online you will find conflicting numbers, a few popular ones are off by a full size. That usually happens when a chart is copied and a row slips, or when diameter and circumference get mixed up. Because every value here is computed from the same inner-circumference source and cross-checked against known jeweller measurements (a US 7 is 17.3 mm across), the columns can’t drift out of step.
Convert a specific size
Prefer to type it in? Use the converter, it handles half sizes and “between sizes” cases.
Frequently asked questions
How is a ring size measured?
A ring size is defined by the space inside the band. Two measurements describe it: the inner diameter (straight across) and the inner circumference (all the way around). Circumference = diameter × π (3.1416). Every national sizing system is built on one of these two numbers.
What size is a 54 mm ring?
A ring with a 54 mm inner circumference is an EU/ISO 54, a US 7, and a UK N½. Its inner diameter is about 17.2 mm (0.68 in), and 54 mm is roughly 2.13 in around.
Which ring size chart is correct?
A correct chart keeps every column aligned to the same inner circumference. This chart is generated from the ISO 8653 formula (circumference = 2.55 × US + 36.5) and the Japanese JIS diameter standard, so the rows never drift apart.
Next: how to measure your ring size at home or try the on-screen ring sizer.