Each system gets the size closest to your number. If your number is past the end of a chart, you'll see Off chart instead of a made up size. A US 7, for example, is 17.3 mm across the inside and 54.4 mm around, which is a UK N½, an EU 54 and a Japanese 14.
Two ways to measure at home
Measure a ring you own
This is the more reliable way, as long as the ring fits the finger you're sizing.
- Lay the ring flat on a ruler marked in millimeters.
- Measure straight across the inside, at the widest point, from one inner edge to the other. Don't include the metal.
- Type that number above with the inside diameter picked. If you have calipers, use them, since they're easier to read than a ruler.
Measure your finger with a strip of paper
- Cut a thin strip of paper about 1 cm wide. Paper works better than string, because string stretches.
- Wrap it around the base of your finger, snug but not tight. It should still slide over your knuckle.
- Mark where the end overlaps, then lay the strip flat and measure from the end to your mark.
- Pick the distance around above and type that number.
Fingers change during the day. They're smaller in the cold and in the morning, and bigger when you're warm. Measure two or three times, at a normal temperature, and if your knuckle is much bigger than the base of your finger, measure both and pick a size between. A wide band feels tighter than a thin one, so if you land between two sizes and the band is wide, go with the bigger one.
Ring size chart
Every US whole and half size from 0 to 16, with the inside diameter, the inside circumference and the nearest size in the other systems. The numbers are rounded to a tenth of a millimeter.
| US | Across mm | Around mm | UK | EU | Japan |
|---|---|---|---|---|---|
| 0 | 11.6 | 36.5 | off chart | off chart | off chart |
| 0.5 | 12.0 | 37.8 | A½ | 38 | off chart |
| 1 | 12.4 | 39.1 | B½ | 39 | off chart |
| 1.5 | 12.9 | 40.4 | C½ | 40 | 1 |
| 2 | 13.3 | 41.7 | D½ | 42 | 2 |
| 2.5 | 13.7 | 42.9 | E½ | 43 | 3 |
| 3 | 14.1 | 44.2 | F½ | 44 | 4 |
| 3.5 | 14.5 | 45.5 | G½ | 45 | 5 |
| 4 | 14.9 | 46.8 | H½ | 47 | 7 |
| 4.5 | 15.3 | 48.0 | I½ | 48 | 8 |
| 5 | 15.7 | 49.3 | J½ | 49 | 9 |
| 5.5 | 16.1 | 50.6 | K½ | 51 | 10 |
| 6 | 16.5 | 51.9 | L½ | 52 | 12 |
| 6.5 | 16.9 | 53.1 | M½ | 53 | 13 |
| 7 | 17.3 | 54.4 | N½ | 54 | 14 |
| 7.5 | 17.7 | 55.7 | O½ | 56 | 15 |
| 8 | 18.1 | 57.0 | P½ | 57 | 16 |
| 8.5 | 18.5 | 58.3 | Q½ | 58 | 18 |
| 9 | 18.9 | 59.5 | R½ | 60 | 19 |
| 9.5 | 19.4 | 60.8 | S½ | 61 | 20 |
| 10 | 19.8 | 62.1 | T½ | 62 | 21 |
| 10.5 | 20.2 | 63.4 | U½ | 63 | 23 |
| 11 | 20.6 | 64.6 | V½ | 65 | 24 |
| 11.5 | 21.0 | 65.9 | W½ | 66 | 25 |
| 12 | 21.4 | 67.2 | Y | 67 | 26 |
| 12.5 | 21.8 | 68.5 | Z | 68 | 27 |
| 13 | 22.2 | 69.7 | Z+1 | 70 | 29 |
| 13.5 | 22.6 | 71.0 | Z+2 | 71 | 30 |
| 14 | 23.0 | 72.3 | Z+3 | 72 | off chart |
| 14.5 | 23.4 | 73.6 | Z+4 | 74 | off chart |
| 15 | 23.8 | 74.8 | Z+5 | 75 | off chart |
| 15.5 | 24.2 | 76.1 | Z+6 | 76 | off chart |
| 16 | 24.6 | 77.4 | off chart | 77 | off chart |
Every UK size, A to Z+6
| UK | Across mm | Around mm | US | EU | Japan |
|---|---|---|---|---|---|
| A | 11.9 | 37.5 | 0.5 | 38 | off chart |
| A½ | 12.1 | 38.1 | 0.5 | 38 | off chart |
| B | 12.3 | 38.8 | 1 | 39 | off chart |
| B½ | 12.5 | 39.4 | 1 | 39 | off chart |
| C | 12.7 | 40.0 | 1.5 | 40 | off chart |
| C½ | 12.9 | 40.6 | 1.5 | 41 | 1 |
| D | 13.1 | 41.3 | 2 | 41 | 1 |
| D½ | 13.3 | 41.9 | 2 | 42 | 2 |
| E | 13.5 | 42.5 | 2.5 | 42 | 3 |
| E½ | 13.7 | 43.1 | 2.5 | 43 | 3 |
| F | 13.9 | 43.8 | 3 | 44 | 4 |
| F½ | 14.1 | 44.4 | 3 | 44 | 4 |
| G | 14.3 | 45.0 | 3.5 | 45 | 5 |
| G½ | 14.5 | 45.6 | 3.5 | 46 | 6 |
| H | 14.7 | 46.3 | 4 | 46 | 6 |
| H½ | 14.9 | 46.9 | 4 | 47 | 7 |
| I | 15.1 | 47.5 | 4.5 | 47 | 7 |
| I½ | 15.3 | 48.1 | 4.5 | 48 | 8 |
| J | 15.5 | 48.8 | 5 | 49 | 9 |
| J½ | 15.7 | 49.4 | 5 | 49 | 9 |
| K | 15.9 | 50.0 | 5.5 | 50 | 10 |
| K½ | 16.1 | 50.6 | 5.5 | 51 | 10 |
| L | 16.3 | 51.3 | 6 | 51 | 11 |
| L½ | 16.5 | 51.9 | 6 | 52 | 12 |
| M | 16.7 | 52.5 | 6 | 52 | 12 |
| M½ | 16.9 | 53.1 | 6.5 | 53 | 13 |
| N | 17.1 | 53.8 | 6.5 | 54 | 13 |
| N½ | 17.3 | 54.4 | 7 | 54 | 14 |
| O | 17.5 | 55.0 | 7 | 55 | 15 |
| O½ | 17.7 | 55.6 | 7.5 | 56 | 15 |
| P | 17.9 | 56.3 | 7.5 | 56 | 16 |
| P½ | 18.1 | 56.9 | 8 | 57 | 16 |
| Q | 18.3 | 57.5 | 8 | 58 | 17 |
| Q½ | 18.5 | 58.1 | 8.5 | 58 | 18 |
| R | 18.7 | 58.8 | 8.5 | 59 | 18 |
| R½ | 18.9 | 59.4 | 9 | 59 | 19 |
| S | 19.1 | 60.0 | 9 | 60 | 19 |
| S½ | 19.3 | 60.6 | 9.5 | 61 | 20 |
| T | 19.5 | 61.3 | 9.5 | 61 | 20 |
| T½ | 19.7 | 61.9 | 10 | 62 | 21 |
| U | 19.9 | 62.5 | 10 | 62 | 22 |
| U½ | 20.1 | 63.1 | 10.5 | 63 | 22 |
| V | 20.3 | 63.8 | 10.5 | 64 | 23 |
| V½ | 20.5 | 64.4 | 11 | 64 | 23 |
| W | 20.7 | 65.0 | 11 | 65 | 24 |
| W½ | 20.9 | 65.6 | 11.5 | 66 | 25 |
| X | 21.1 | 66.3 | 11.5 | 66 | 25 |
| X½ | 21.3 | 66.9 | 12 | 67 | 26 |
| Y | 21.5 | 67.5 | 12 | 67 | 26 |
| Y½ | 21.7 | 68.1 | 12.5 | 68 | 27 |
| Z | 21.9 | 68.8 | 12.5 | 69 | 28 |
| Z+1 | 22.3 | 70.0 | 13 | 70 | 29 |
| Z+2 | 22.7 | 71.3 | 13.5 | 71 | 30 |
| Z+3 | 23.1 | 72.5 | 14 | 72 | off chart |
| Z+4 | 23.5 | 73.8 | 14.5 | 74 | off chart |
| Z+5 | 23.9 | 75.0 | 15 | 75 | off chart |
| Z+6 | 24.3 | 76.3 | 15.5 | 76 | off chart |
Every Japanese size, 1 to 30
| Japan | Across mm | Around mm | US | UK | EU |
|---|---|---|---|---|---|
| 1 | 13.0 | 40.8 | 1.5 | C½ | 41 |
| 2 | 13.3 | 41.9 | 2 | D½ | 42 |
| 3 | 13.7 | 42.9 | 2.5 | E½ | 43 |
| 4 | 14.0 | 44.0 | 3 | F | 44 |
| 5 | 14.3 | 45.0 | 3.5 | G | 45 |
| 6 | 14.7 | 46.1 | 3.5 | H | 46 |
| 7 | 15.0 | 47.1 | 4 | H½ | 47 |
| 8 | 15.3 | 48.2 | 4.5 | I½ | 48 |
| 9 | 15.7 | 49.2 | 5 | J½ | 49 |
| 10 | 16.0 | 50.3 | 5.5 | K | 50 |
| 11 | 16.3 | 51.3 | 6 | L | 51 |
| 12 | 16.7 | 52.4 | 6 | M | 52 |
| 13 | 17.0 | 53.4 | 6.5 | M½ | 53 |
| 14 | 17.3 | 54.5 | 7 | N½ | 54 |
| 15 | 17.7 | 55.5 | 7.5 | O½ | 56 |
| 16 | 18.0 | 56.5 | 8 | P | 57 |
| 17 | 18.3 | 57.6 | 8 | Q | 58 |
| 18 | 18.7 | 58.6 | 8.5 | R | 59 |
| 19 | 19.0 | 59.7 | 9 | S | 60 |
| 20 | 19.3 | 60.7 | 9.5 | S½ | 61 |
| 21 | 19.7 | 61.8 | 10 | T½ | 62 |
| 22 | 20.0 | 62.8 | 10.5 | U½ | 63 |
| 23 | 20.3 | 63.9 | 10.5 | V | 64 |
| 24 | 20.7 | 64.9 | 11 | W | 65 |
| 25 | 21.0 | 66.0 | 11.5 | X | 66 |
| 26 | 21.3 | 67.0 | 12 | X½ | 67 |
| 27 | 21.7 | 68.1 | 12.5 | Y½ | 68 |
| 28 | 22.0 | 69.1 | 13 | Z | 69 |
| 29 | 22.3 | 70.2 | 13 | Z+1 | 70 |
| 30 | 22.7 | 71.2 | 13.5 | Z+2 | 71 |
How each system works
- US and Canada. Size 0 is 0.458 inches across the inside, and each whole size adds 0.032 inches, about 0.81 mm. A half size adds 1.28 mm around.
- UK, Ireland and Australia. Letters from A to Z, with half letters. Under the British Standard BS 6820:1987, size C is 40 mm around and each letter adds 1.25 mm, so a half letter is 0.625 mm. Past Z the sizes go on as Z+1 up to Z+6.
- EU. The ISO 8653 standard uses the inside circumference in millimeters as the size, so an EU 54 is 54 mm around.
- Japan. Size 1 is 13 mm across, and each size adds a third of a millimeter, about 1.05 mm around.
Why charts don't always agree
Size charts from different shops can be off from each other by a half size, and it's usually not a mistake. Some UK charts still follow an older standard from before 1987. Others round every size to the nearest row they have.
Take a US 7. It's 54.42 mm around. Under BS 6820, UK N½ is 54.38 mm and O is 55.00 mm, so the US 7 is right on top of N½. The Jewellerybox chart below lists a US 7 as an O, though. When a size falls this close to the line, ask the shop which chart they use, or check the millimeters, since those don't change.
German and Swiss shops often use their own numbers too. On the Jewellerybox chart, the German sizes match the inside diameter in millimeters.
Why there's no printable ring sizer here
A paper sizer only works if it prints at exactly 100 percent. Many printers and print windows shrink the page to fit the paper, and you can't see it happen. If a page prints just 3 percent small, a US 7 comes out 1.6 mm short around, which is more than a US half size. So rather than give you a sizer that might be wrong, I'd point you to the ruler and paper strip above, or to a jeweler, who can measure you with real sizing rings in a minute.
Questions
What is a size 7 ring in mm?
It's 17.3 mm across the inside and 54.4 mm around. That's an EU 54, a Japanese 14 and a UK N½.
How do I convert a UK ring size to US?
Pick a ring size above, choose UK and your letter, and the US size shows up next to it. The UK chart above has every letter with its US size too.
Is the EU size the same as the circumference?
Yes. Under ISO 8653, the size is the inside circumference in millimeters, so a 52 is 52 mm around the inside.
What if I'm between two sizes?
Go with the bigger one if the band is wide, since wide bands feel tighter. For a thin band, measure again on a warm day, or try both sizes on in a shop if you can.
Is there an app for this?
I'm working on a ring sizer for Android that measures a ring you hold on the screen. It isn't out yet. When it is, you'll find it on my apps page.
Sources
- Wikipedia, Ring size. The US steps of 0.032 inches from 0.458 inches at size 0, and the UK scale from BS 6820:1987, with C at 40 mm and 1.25 mm a letter.
- ISO, ISO 8653:2016, Jewellery, ring sizes, definition, measurement and designation. The ring size as the inside circumference in millimeters.
- Jewellerybox, ring size guide. A UK jeweler's chart in millimeters, used to check the US and UK rows.
- moocota, ring size list (in Japanese). Japanese sizes 1 to 30 with the inside diameter and circumference.