Ring Size Chart
This chart estimates conversions between supported US, UK, EU/ISO, Japanese, and Indian sizes. In our nominal reference, a US size 7 maps to 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.
Published by Ring Sizer · App developer: Pawel Boguta · Updated
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
- 14
- India
- 14
- Diameter
- 17.2 mm
- Circumference (mm)
- 54.0 mm
- Circumference (in)
- 2.126 in
Uses the Ring Sizer conversion model. Measured values and nominal size conversions can round differently. Use thin band for a chart conversion. See our methodology and supported ranges.
Full ring size chart
Each row starts from a nominal US half size, with no band-width adjustment. — means a regional reference is unavailable. A measured diameter can round to the same US label while producing a different circumference-based size.
| US | Inner diameter | Inner circumference | UK | EU / ISO | Japan | India |
|---|---|---|---|---|---|---|
| 3 | 14.1 mm | 44.2 mm | — | 44 | 4 | 4 |
| 3.5 | 14.5 mm | 45.5 mm | — | 45 | 5 | 5 |
| 4 | 14.9 mm | 46.8 mm | H | 47 | 7 | 7 |
| 4.5 | 15.3 mm | 48.0 mm | I | 48 | 8 | 8 |
| 5 | 15.7 mm | 49.3 mm | J 1/2 | 49 | 9 | 9 |
| 5.5 | 16.1 mm | 50.6 mm | K 1/2 | 51 | 10 | 11 |
| 6 | 16.5 mm | 51.9 mm | L 1/2 | 52 | 12 | 12 |
| 6.5 | 16.9 mm | 53.1 mm | M 1/2 | 53 | 13 | 13 |
| 7 | 17.3 mm | 54.4 mm | N 1/2 | 54 | 14 | 14 |
| 7.5 | 17.7 mm | 55.7 mm | O 1/2 | 56 | 15 | 16 |
| 8 | 18.1 mm | 57.0 mm | P 1/2 | 57 | 17 | 17 |
| 8.5 | 18.5 mm | 58.2 mm | Q 1/2 | 58 | 18 | 18 |
| 9 | 18.9 mm | 59.5 mm | R 1/2 | 60 | 19 | 20 |
| 9.5 | 19.4 mm | 60.8 mm | S 1/2 | 61 | 21 | 21 |
| 10 | 19.8 mm | 62.1 mm | T 1/2 | 62 | 22 | 22 |
| 10.5 | 20.2 mm | 63.3 mm | U 1/2 | 63 | 23 | 23 |
| 11 | 20.6 mm | 64.6 mm | V 1/2 | 65 | 24 | 25 |
| 11.5 | 21.0 mm | 65.9 mm | W 1/2 | 66 | 26 | 26 |
| 12 | 21.4 mm | 67.2 mm | Y | 67 | 27 | 27 |
| 12.5 | 21.8 mm | 68.5 mm | Z | 68 | — | 28 |
| 13 | 22.2 mm | 69.7 mm | Z+1 | 70 | — | 30 |
| 13.5 | 22.6 mm | 71.0 mm | — | 71 | — | 31 |
| 14 | 23.0 mm | 72.3 mm | — | 72 | — | 32 |
| 14.5 | 23.4 mm | 73.6 mm | — | 74 | — | 34 |
| 15 | 23.8 mm | 74.8 mm | — | 75 | — | 35 |
Japanese ring size to US
Our Japanese reference matches the nearest listed diameter. To estimate a Japanese ring size in US, find it below and read across: Japan 14 is about US 7, Japan 9 is about US 5, and Japan 19 is about US 9.
| Japan | US | UK | EU |
|---|---|---|---|
| 7 | 4 | H | 47 |
| 9 | 5 | J 1/2 | 49 |
| 12 | 6 | L 1/2 | 52 |
| 14 | 7 | N 1/2 | 54 |
| 17 | 8 | P 1/2 | 57 |
| 19 | 9 | R 1/2 | 60 |
| 22 | 10 | T 1/2 | 62 |
| 24 | 11 | V 1/2 | 65 |
| 27 | 12 | Y | 67 |
UK to US ring size
UK and Australian sizes use letters. To convert a UK ring size to US, match the letter below: UK J 1/2 is about US 5, UK L 1/2 is about US 6, UK N 1/2 is about US 7, and UK T 1/2 is about US 10. Roughly two UK letter steps equal one US size.
| UK | US | EU | Diameter |
|---|---|---|---|
| H | 4 | 47 | 14.9 mm |
| J 1/2 | 5 | 49 | 15.7 mm |
| L 1/2 | 6 | 52 | 16.5 mm |
| N 1/2 | 7 | 54 | 17.3 mm |
| P 1/2 | 8 | 57 | 18.1 mm |
| R 1/2 | 9 | 60 | 18.9 mm |
| T 1/2 | 10 | 62 | 19.8 mm |
| V 1/2 | 11 | 65 | 20.6 mm |
| Y | 12 | 67 | 21.4 mm |
Need to go the other way or convert another system? Use the ring size converter.
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. EU output rounds inner circumference to a whole millimeter; our Japanese reference matches the nearest listed diameter. India tracks circumference, where the size is roughly the inner circumference in millimeters minus 40. These are the Ring Sizer model conventions. Retailer charts can differ; see our methodology for rounding and supported ranges.
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.
- What is a Japanese ring size in US?
- Our Japanese reference uses the nearest listed diameter. Retailer conventions can differ. Japan 14 is about US 7, Japan 9 is about US 5, and Japan 19 is about US 9. Find your Japanese size in the chart and read across to the US column.
- How do I convert a UK ring size to US?
- UK uses letters. UK J 1/2 is about US 5, UK L 1/2 is about US 6, UK N 1/2 is about US 7, and UK T 1/2 is about US 10. Each US size is roughly two UK letter steps.
Sources and methodology
Read our conversion rules, supported ranges, and measurement limitations.
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 Ring Sizer app, free to download with in-app purchases.
Download Ring Sizer- Free download · In-app purchases
- iOS
- No sign-up
- Works offline
