International Ring Size Conversion
Find your size on your phone
About a minute. All you need is a card and a ring that fits.
1 Calibrate your screen
Hold any bank or ID card against the screen, long side along the bar. Drag the slider until the bar is exactly as long as the card. You only do this once.
2 Lay a ring that fits flat on the screen
Drag the slider until the circle lines up with the inside edge of the ring.
Inside measurements of the band.
| US size | Inside diameter | Circumference |
|---|
A Measure a ring that fits
Lay it flat and measure straight across the inside edge at its widest point, in millimeters. Find it in the size chart.
B Use a strip of paper
Cut a strip about 5 mm wide, wrap it snugly around the base of the finger, mark the overlap and measure to the mark. That is the circumference. Don't use string, it stretches.
Tips: measure at the end of the day when hands are warm; between two sizes, choose the larger; keeping it a surprise, borrow a ring she wears on that finger.
Contact us and we'll help you find it before anything is made.
Ring sizing systems differ by country, but they all describe the same physical thing: the inside circumference of the band in millimeters. Convert by finding your millimeter measurement, not by converting number to number — that is where mistakes creep in.
We size in US measurements. If you have a size from another system, use the chart below to find its US equivalent before ordering.
Conversion chart
| US / Canada | UK / Australia | Europe (ISO) | Japan / China | Diameter (mm) | Circumference (mm) |
|---|---|---|---|---|---|
| 3 | F | 44 | 4 | 14.1 | 44.2 |
| 3.5 | G | 45½ | 5 | 14.5 | 45.5 |
| 4 | H | 47 | 7 | 14.9 | 46.8 |
| 4.5 | I | 48 | 8 | 15.3 | 48.0 |
| 5 | J½ | 49½ | 9 | 15.7 | 49.3 |
| 5.5 | K½ | 50½ | 10 | 16.1 | 50.6 |
| 6 | L½ | 52 | 11 | 16.5 | 51.9 |
| 6.5 | M½ | 53 | 13 | 16.9 | 53.1 |
| 7 | N½ | 54½ | 14 | 17.3 | 54.4 |
| 7.5 | O½ | 55½ | 15 | 17.7 | 55.7 |
| 8 | P½ | 57 | 16 | 18.1 | 57.0 |
| 8.5 | Q½ | 58 | 17 | 18.5 | 58.3 |
| 9 | R½ | 59½ | 18 | 19.0 | 59.5 |
| 9.5 | S½ | 61 | 19 | 19.4 | 60.8 |
| 10 | T½ | 62 | 20 | 19.8 | 62.1 |
| 10.5 | U½ | 63½ | 22 | 20.2 | 63.4 |
| 11 | V½ | 64½ | 23 | 20.6 | 64.6 |
| 11.5 | W½ | 66 | 24 | 21.0 | 65.9 |
| 12 | X½ | 67 | 25 | 21.4 | 67.2 |
| 12.5 | Y½ | 68½ | 26 | 21.8 | 68.5 |
| 13 | Z½ | 70 | 27 | 22.2 | 69.7 |
How each system works
- US and Canada use a numeric scale in half-size steps. Each full size is roughly 0.4 mm of diameter, or about 1.3 mm of circumference.
- UK, Ireland, Australia and New Zealand use letters, with half sizes marked by a ½. The alphabet runs from A upward, so a UK L½ is a US 6.
- Europe (ISO 8653) is the most literal: the number is the inside circumference in millimeters, rounded. A European 52 is a band 52 mm around.
- Japan and China use their own numeric scale, which does not map evenly onto the others. Treat these as the closest match rather than an exact equivalent, and confirm against the millimeter columns.
Convert by millimeters, not by number
Systems round differently, and rounding twice compounds the error. If you know your size in one system, read across to the millimeter columns first, then find the nearest US size to that measurement. Where a measurement falls between two sizes, go up rather than down — a loose ring can be taken in, a ring that will not clear the knuckle cannot be worn.
Do not have a size in any system? Measure it at home in about five minutes.
Frequently asked questions
What is a UK size L in US sizing?
A UK L½ is a US 6, the most common women's size, with an inside diameter of 16.5 mm. A plain UK L sits just below that, between a US 5.5 and a US 6.
What does a European ring size number mean?
Under ISO 8653, the European size is the inside circumference of the band in millimeters. A European 52 is a ring measuring 52 mm around the inside, which corresponds to a US 6.
Are Japanese ring sizes the same as US sizes?
No. Japan uses a separate numeric scale that does not increase in step with the US one — a Japanese 11 is a US 6, but a Japanese 20 is a US 10. Always confirm against the millimeter measurement rather than assuming the numbers align.
How much bigger is a half size?
About 0.2 mm of inside diameter, or roughly 0.65 mm of circumference. It is a small difference on paper and a noticeable one on the finger.
Which sizes do you make?
Every ring is made in US half sizes from 3 to 13. Sizes outside that range are available on request — call (888) 709-7077.
