Ring size converter
Convert a ring size between countries, work it out from a finger or from a ring that already fits, and print a true-scale sizer to check at home. Every size is defined by the inside of the ring, so results are in millimetres too.
US / Canada 7 has an inside circumference of 54.4 mm (diameter 17.32 mm)
- US / CA7
- UK / AUN½
- ISO / EU54
- CH / IT / ES14
- JP14
- Diameter17.32 mm
Ring sizes are defined by the inside of the ring. Comfort-fit and very wide bands feel different, so ask the jeweller whether they suggest a different size for that design.
Printable ring sizer
- Press Print ring sizer. In the print dialog choose 100 % or Actual size and turn off Fit to page or Shrink to fit. A4 and US Letter both work.
- Before you use the sheet, lay a real ruler on the 10 cm and 4 in rulers at the top. If either is off by more than a millimetre, the printer has scaled the page: print again or use the downloaded SVG.
- Use the strip to measure a finger, or the circles to size a ring that already fits. When they disagree, trust the ring.
Ring size chart
US half sizes with every other system; the closest row is highlighted.
| US / CA | UK / AU | ISO / EU | CH / IT | JP | Diameter (mm) | Circumference (mm) |
|---|---|---|---|---|---|---|
| 2 | D½ | 42 | 2 | 2 | 13.26 | 41.7 |
| 2½ | E½ | 43 | 3 | 3 | 13.67 | 42.9 |
| 3 | F½ | 44 | 4 | 4 | 14.07 | 44.2 |
| 3½ | G½ | 45 | 5 | 5 | 14.48 | 45.5 |
| 4 | H½ | 47 | 7 | 7 | 14.88 | 46.8 |
| 4½ | I½ | 48 | 8 | 8 | 15.29 | 48 |
| 5 | J½ | 49 | 9 | 9 | 15.7 | 49.3 |
| 5½ | K½ | 51 | 11 | 10 | 16.1 | 50.6 |
| 6 | L½ | 52 | 12 | 12 | 16.51 | 51.9 |
| 6½ | M½ | 53 | 13 | 13 | 16.92 | 53.1 |
| 7 | N½ | 54 | 14 | 14 | 17.32 | 54.4 |
| 7½ | O½ | 56 | 16 | 15 | 17.73 | 55.7 |
| 8 | P½ | 57 | 17 | 16 | 18.14 | 57 |
| 8½ | Q½ | 58 | 18 | 18 | 18.54 | 58.3 |
| 9 | R½ | 60 | 20 | 19 | 18.95 | 59.5 |
| 9½ | S½ | 61 | 21 | 20 | 19.35 | 60.8 |
| 10 | T½ | 62 | 22 | 21 | 19.76 | 62.1 |
| 10½ | U½ | 63 | 23 | 23 | 20.17 | 63.4 |
| 11 | V½ | 65 | 25 | 24 | 20.57 | 64.6 |
| 11½ | W½ | 66 | 26 | 25 | 20.98 | 65.9 |
| 12 | Y | 67 | 27 | 26 | 21.39 | 67.2 |
| 12½ | Z | 68 | 28 | 27 | 21.79 | 68.5 |
| 13 | Z+1 | 70 | 30 | 29 | 22.2 | 69.7 |
| 13½ | Z+2 | 71 | 31 | 30 | 22.61 | 71 |
| 14 | Z+3 | 72 | 32 | 31 | 23.01 | 72.3 |
| 14½ | Z+4 | 74 | 34 | 32 | 23.42 | 73.6 |
| 15 | Z+5 | 75 | 35 | 33 | 23.83 | 74.8 |
How to use it
A ring size: pick the system the jeweller uses and the size; the strips show the same ring in every other system, with its inside diameter. My finger: enter the distance around the finger in millimetres or inches. A ring I own: enter the inside diameter of a ring that fits the same finger.
The systems: ISO 8653, used in France, the Nordic countries and much of Europe, simply states the inside circumference in millimetres. Swiss, Italian and Spanish sizes are that number minus 40. US sizes grow by 0.8128 mm of diameter per size, UK and Australian letters by 1.25 mm of circumference per letter, and Japanese numbers by about ⅓ mm of diameter.
Getting a good reading: fingers are larger when warm and late in the day, and smaller in the cold. Measure two or three times and use the middle value. If your knuckle is much wider than the base of the finger, the ring has to pass it: pick a size between the two measurements.
Worked example: a US 7 has an inside diameter of 17.32 mm and a circumference of 54.4 mm. That is UK N½, ISO 54, Swiss 14 and Japanese 14.
Sources
- ISO, ISO 8653:2016 Jewellery – Ring-sizes – Definition, measurement and designation.
- Ring size (Wikipedia): the US definition (0.458 in + 0.032 in per size, inside diameter), British Standard 6820:1987 for UK letters, and the Swiss/Italian circumference − 40 rule.
- Moocota, Japanese ring size table (号): size 1 = 13.0 mm inside diameter, then about 0.33 mm per size.
Questions
How can I find my ring size at home?
Either lay a ring that already fits on the printable circle chart, or measure the finger with the paper strip from the same sheet. A strip of paper and a ruler work too: wrap, mark, measure the length in millimetres and enter it as My finger. A ring that fits is the more reliable of the two.
Will the printed sizer be accurate?
Only if it prints at full size. Many print dialogs shrink pages to fit the margins by default, so choose 100 % or Actual size and then check the 10 cm and 4 in rulers on the sheet with a real ruler. If they match, the strip and circles are true to scale.
What size is a US 7 in the UK and Europe?
A US 7 is UK N½, ISO 54 (France, Germany and most of Europe), Swiss or Italian 14 and Japanese 14. Its inside is 17.3 mm across and 54.4 mm around.
How tight should a ring be?
It should slide over the knuckle with a little resistance and then sit without spinning or sliding off when you shake your hand. If it leaves a deep mark or you need soap to remove it, it is too small.
Do wide bands need a bigger size?
Often, yes. A wide band covers more of the finger and feels tighter than a slim one of the same inside size, so jewellers commonly suggest going up a quarter or half US size for wide bands. Ask the maker, because comfort-fit bands with a rounded inside behave differently.
What is ISO 8653?
The international standard for ring sizes. It defines the size as the inside circumference of the ring in millimetres, so ISO 52 is 52 mm around the inside. France, the Nordic countries and many other European countries label rings this way.