Ring Size Chart
This ring size chart converts any size between the US, UK, EU/ISO, Japanese, and Indian systems. A US size 7, for example, equals UK N 1/2, EU 54, and an inner diameter of about 17.3 mm. Find your size in any one system and read across its row to get every other, or enter a millimeter measurement below to compute your size instantly.
This article is for anyone converting a known size or a measurement into the system a retailer uses.
Convert a measurement to a ring size
54 mm circumference is about US 7, UK N 1/2, EU 54.
Thin band chart size, with no fit adjustment.
Converted sizes
- US / Canada
- 7
- UK / Australia
- N 1/2
- EU / ISO
- 54
- Japan / China
- 14
- India
- 14
- Diameter
- 17.2 mm
- Circumference (mm)
- 54.0 mm
- Circumference (in)
- 2.126 in
Computed with the same conversion engine as the Ring Sizer app. Use thin band for pure chart conversion; use a wider band when you want a fit recommendation.
Full ring size chart
| US | Inner diameter | Inner circumference | UK | EU / ISO | Japan | India |
|---|---|---|---|---|---|---|
| 3 | 14.0 mm | 44.0 mm | H | 44 | 4 | 4 |
| 3.5 | 14.5 mm | 45.6 mm | H | 46 | 5 | 6 |
| 4 | 15.0 mm | 47.1 mm | H | 47 | 7 | 7 |
| 5 | 15.5 mm | 48.7 mm | J 1/2 | 49 | 9 | 9 |
| 5.5 | 16.0 mm | 50.3 mm | K 1/2 | 50 | 10 | 10 |
| 6 | 16.5 mm | 51.8 mm | L 1/2 | 52 | 12 | 12 |
| 6.5 | 17.0 mm | 53.4 mm | M 1/2 | 53 | 13 | 13 |
| 7 | 17.5 mm | 55.0 mm | N 1/2 | 55 | 15 | 15 |
| 8 | 18.0 mm | 56.5 mm | P 1/2 | 57 | 16 | 17 |
| 8.5 | 18.5 mm | 58.1 mm | Q 1/2 | 58 | 18 | 18 |
| 9 | 19.0 mm | 59.7 mm | R 1/2 | 60 | 19 | 20 |
| 9.5 | 19.5 mm | 61.3 mm | S 1/2 | 61 | 21 | 21 |
| 10.5 | 20.0 mm | 62.8 mm | U 1/2 | 63 | 22 | 23 |
| 11 | 20.5 mm | 64.4 mm | V 1/2 | 64 | 24 | 24 |
| 11.5 | 21.0 mm | 66.0 mm | W 1/2 | 66 | 26 | 26 |
| 12 | 21.5 mm | 67.5 mm | Y | 68 | 27 | 28 |
| 13 | 22.0 mm | 69.1 mm | Z+1 | 69 | 27 | 29 |
| 13.5 | 22.5 mm | 70.7 mm | Z+1 | 71 | 27 | 31 |
| 14 | 23.0 mm | 72.3 mm | Z+1 | 72 | 27 | 32 |
| 14.5 | 23.5 mm | 73.8 mm | Z+1 | 74 | 27 | 34 |
| 15 | 24.0 mm | 75.4 mm | Z+1 | 75 | 27 | 35 |
How to use this chart
To find your size, first measure your ring size by reading the inner diameter or inner circumference of a ring in millimeters. Find the closest value in the chart, then read across that row to get the equivalent size in every other system. Each full US size is only about 0.81 mm of diameter, so measuring twice and averaging helps you land on the right row.
How these conversions are computed
US sizes come from a linear fit of inner diameter, about 0.81 mm of diameter per full size. The EU/ISO number is simply the inner circumference in millimeters (ISO 8653), and Japan, China, and Korea share the JIS scale, matched here by nearest diameter. India tracks circumference, where the size is roughly the inner circumference in millimeters minus 40. The same conversion engine that produces this chart powers the Ring Sizer app, so the numbers here match the numbers you see in the app.
Frequently asked questions
- What ring size is 18 mm?
- An inner diameter of 18 mm is about a US size 8, which is UK P 1/2 and EU 57. Measure the inside of the band straight across the center to get the diameter.
- Is a US ring size the same as the EU size?
- No. US sizes are numbers from a diameter scale, while the EU/ISO size is the inner circumference in millimeters. A US 7 is an EU 54.
- How do I read a ring size chart?
- Find your measurement or known size in one column, then read across that row to see the equivalent in every other system. If you are between two rows, round up.
Get your exact size, without the jeweler
This chart converts a size you already have. To find your real size in the first place, measure it right on screen and see every system at once, the most accurate option short of a trip to the jeweler, with the free Ring Sizer app.
Download Ring Sizer- Free
- iOS
- No sign-up
- Works offline
