RING SIZE CHART
Every size, every region, one table.
Diameter is the inner edge of the ring, straight across. Circumference is the distance around the inside. If you know either one, find the row it falls closest to.
| US / CA | UK / AU | EU | India | Japan | China | Diameter (mm) | Circumference (mm) |
|---|---|---|---|---|---|---|---|
| 3 | F | 44 | 4 | 4 | 4 | 14.1 | 44.2 |
| 3.5 | G | 45 | 5 | 5 | 5 | 14.5 | 45.5 |
| 4 | H | 46 | 6 | 7 | 7 | 14.9 | 46.8 |
| 4.5 | I | 47 | 7 | 8 | 8 | 15.3 | 48.0 |
| 5 | J | 49 | 8 | 9 | 9 | 15.7 | 49.3 |
| 5.5 | K | 50 | 9 | 10 | 10 | 16.1 | 50.6 |
| 6 | L | 51 | 10 | 12 | 12 | 16.5 | 51.9 |
| 6.5 | M | 52 | 11 | 13 | 13 | 16.9 | 53.1 |
| 7 | N | 54 | 13 | 14 | 14 | 17.3 | 54.4 |
| 7.5 | O | 55 | 14 | 15 | 15 | 17.7 | 55.7 |
| 8 | P | 56 | 15 | 16 | 16 | 18.1 | 57.0 |
| 8.5 | Q | 57 | 16 | 17 | 17 | 18.5 | 58.3 |
| 9 | R | 59 | 17 | 18 | 18 | 18.9 | 59.5 |
| 9.5 | S | 60 | 18 | 19 | 19 | 19.3 | 60.8 |
| 10 | T | 61 | 19 | 20 | 20 | 19.8 | 62.1 |
| 10.5 | U | 62 | 20 | 21 | 21 | 20.2 | 63.4 |
| 11 | V | 64 | 21 | 22 | 22 | 20.6 | 64.6 |
| 11.5 | W | 65 | 22 | 23 | 23 | 21.0 | 65.9 |
| 12 | X | 66 | 24 | 24 | 24 | 21.4 | 67.2 |
| 12.5 | Y | 67 | 25 | 25 | 25 | 21.8 | 68.5 |
| 13 | Z | 69 | 26 | 26 | 26 | 22.2 | 69.7 |
| 13.5 | Z1 | 70 | 27 | 27 | 27 | 22.6 | 71.0 |
Reading between rows
If your measurement lands between two rows, the calculator on the home page interpolates automatically. By hand, round to the nearer diameter, and round up rather than down if you're unsure, a slightly loose ring is easier to live with than a tight one.
Why regions don't line up perfectly
US and UK sizes use fixed diameter steps. EU, Japan, and China sizes are closer to raw circumference, so the gap between adjacent sizes isn't always constant. That's why the same physical ring can be an exact US 7 but sit between two Japan sizes.
How to use this chart
- Find the measurement you already have: inner diameter in millimeters, inner circumference in millimeters, or a size in one region.
- Look along that row to read the matching sizes in the other regions.
- If your number falls between two rows, take the nearer one, or the larger if you are unsure.
Converting by formula
The US scale moves in even steps, so you can estimate the inner diameter of a size directly: diameter in millimeters is roughly 11.63 plus 0.8128 times the US size. A US 7 works out to about 17.3 mm, and a US 10 to about 19.8 mm, which matches the table. Circumference is the diameter multiplied by pi (3.1416).
Worked examples using the table above:
- Diameter 17.0 mm: closer to US 6.5 (16.9 mm) than to US 7 (17.3 mm).
- Circumference 54 mm: about US 7, UK N and EU 54.
- UK size P: US 8, with an inner diameter of 18.1 mm.
How the regional scales differ
US and UK sizes move in steady steps, and each UK letter lines up with roughly one US half size in this table. EU sizes are based on circumference in millimeters. Japan and China use their own whole-number scales, and India's numbering varies a little between jewelers. Because the steps are not identical, an exact US half size can land between two sizes in another system.
Our guide to ring size systems explains each scale in detail.
When the chart is not enough
A conversion chart gives the standard equivalent, but a few things can change the size you should actually buy:
- Band width. Wide bands fit tighter. See wide band sizing.
- Brand sizing. Some brands use their own numbers. Check our Cartier, Tiffany, Pandora and Oura guides.
- Swelling and temperature. See why your ring size changes.
- Measurement errors. Our common mistakes list covers the usual causes of a wrong size.
Ring size chart questions
What size is a 17 mm ring?
A 17 mm inner diameter sits between US 6.5 (16.9 mm) and US 7 (17.3 mm), and is closer to 6.5.
What is a 54 mm ring in US size?
An inner circumference of 54 mm is about a US 7, which is also a UK N and an EU 54.
Is a 6 mm ring the same as a size 6?
No. 6 mm is usually the width of the band, while size 6 is a measure of the inside of the ring. They are unrelated.
Which is more accurate, diameter or circumference?
Both describe the same ring. Diameter is easier to measure on an existing ring, and circumference is easier to measure on a finger. Use whichever you can measure more carefully.