Ring Size Chart – US, UK, EU & MM Conversion
This complete ring size chart converts between every major sizing system: US and Canada, UK and Australia, EU/ISO (used in Germany and most of Europe), Italy/Spain/Switzerland, and Russia. Each row also shows the ring's inner diameter in millimeters, so you can match a measurement you took at home.
Ring sizes are defined by the inner circumference of the band (standardized in ISO 8653) or by the inner diameter. If you have measured a ring or your finger, find the closest millimeter value in the table to read off your size in every system at once.
Ring Size Conversion Chart
| ISO/DE | Inner Diameter | US/CA | UK/AU | IT/ES/CH | RU |
|---|---|---|---|---|---|
| 44 | 14.0 mm | 3 | F | 4 | 14 |
| 45 | 14.3 mm | 3½ | G | 5 | 14.5 |
| 46 | 14.6 mm | 3½ | H | 6 | 14.5 |
| 47 | 15.0 mm | 4 | H½ | 7 | 15 |
| 48 | 15.3 mm | 4½ | I½ | 8 | 15.5 |
| 49 | 15.6 mm | 5 | J | 9 | 15.5 |
| 50 | 15.9 mm | 5½ | K | 10 | 16 |
| 51 | 16.2 mm | 5½ | L | 11 | 16 |
| 52 | 16.6 mm | 6 | L½ | 12 | 16.5 |
| 53 | 16.9 mm | 6½ | M½ | 13 | 17 |
| 54 | 17.2 mm | 7 | N | 14 | 17 |
| 55 | 17.5 mm | 7½ | O | 15 | 17.5 |
| 56 | 17.8 mm | 7½ | P | 16 | 18 |
| 57 | 18.1 mm | 8 | P½ | 17 | 18 |
| 58 | 18.5 mm | 8½ | Q½ | 18 | 18.5 |
| 59 | 18.8 mm | 9 | R | 19 | 19 |
| 60 | 19.1 mm | 9 | S | 20 | 19 |
| 61 | 19.4 mm | 9½ | T | 21 | 19.5 |
| 62 | 19.7 mm | 10 | T½ | 22 | 19.5 |
| 63 | 20.1 mm | 10½ | U½ | 23 | 20 |
| 64 | 20.4 mm | 11 | V | 24 | 20.5 |
| 65 | 20.7 mm | 11 | W | 25 | 20.5 |
| 66 | 21.0 mm | 11½ | X | 26 | 21 |
| 67 | 21.3 mm | 12 | X½ | 27 | 21.5 |
| 68 | 21.6 mm | 12½ | Y½ | 28 | 21.5 |
| 69 | 22.0 mm | 12½ | Z | 29 | 22 |
| 70 | 22.3 mm | 13 | Z½ | 30 | 22.5 |
| 71 | 22.6 mm | 13½ | Z1 | 31 | 22.5 |
| 72 | 22.9 mm | 14 | Z2 | 32 | 23 |
Don't know your size yet?
Use our free online ring sizer to measure a ring or your finger in under a minute — no printing and no app, just a bank card to calibrate your screen.
Measure your ring size nowRing sizes in millimeters and inches
Millimeters are the most reliable way to talk about ring sizes because every regional system can be derived from them. Two measurements matter: the inner diameter (the distance across the inside of the ring at its widest point) and the inner circumference (the distance around the inside edge). They are related by a constant: circumference = diameter × π.
To convert millimeters to inches, divide by 25.4. For example, a US size 7 ring has an inner diameter of about 17.2 mm, which is roughly 0.68 inches, and an inner circumference of about 54 mm (2.13 inches).
US and Canada ring sizes
The North American system uses numbers from about 3 to 13½, with half sizes in between. It is the system you will see on most international jewelry sites. The scale is linear: each full size adds about 2.55 mm of circumference.
If you know a ring's inner circumference in millimeters, you can estimate the US size with the formula: US size = (circumference − 36.5) ÷ 2.55. Our chart already does this math for you, including half sizes.
UK, Ireland and Australia ring sizes
The British system uses letters from A to Z, with half sizes written as A½, B½ and so on. Sizes beyond Z are written Z½, Z1 and Z2. Each letter step corresponds to 1.25 mm of inner circumference.
The same letter system is used in the United Kingdom, Ireland, Australia, New Zealand and South Africa. A typical women's size is around L–N, and a typical men's size is around R–T.
EU, ISO and German ring sizes
Most of continental Europe, including Germany, France and Scandinavia, uses the ISO size: simply the inner circumference in millimeters. A size 54 ring has an inner circumference of 54 mm — nothing to memorize.
Two related systems appear in the chart as well. Italy, Spain and Switzerland use the circumference minus 40 (so ISO 54 = IT 14). Russia traditionally uses the inner diameter in millimeters rounded to the nearest 0.5 (so ISO 54 ≈ RU 17).
Popular sizes quick reference
These are the most commonly purchased ring sizes. If you only remember one number, remember the diameter in millimeters — you can convert it to any system with the full chart above.
| US Size | Inner Diameter | UK Size | EU Size |
|---|---|---|---|
| 5 | 15.6 mm | J | 49 |
| 6 | 16.6 mm | L½ | 52 |
| 7 | 17.2 mm | N | 54 |
| 8 | 18.1 mm | P½ | 57 |
| 9 | 18.8 mm | R | 59 |
| 10 | 19.7 mm | T½ | 62 |
Between two sizes?
If your measurement falls between two sizes, choose the larger one. A slightly loose ring is comfortable and easy to remove; a slightly tight one can pinch, especially in warm weather when fingers swell.
Wide bands (8 mm and wider) fit more snugly than narrow ones because they cover more of the finger. For a wide band, consider going up by a quarter to a half size from your measured size.