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What is it in the other system?
Your US size — or your finger measurement in millimetres — and the full cross-reference.
REFERENCE CHART · EVERYDAY
Ring Size Conversion Chart
The US uses numbers, the UK uses letters, Europe uses millimetres, and Japan uses its own numbers — but they all describe the same thing: the inside circumference of the ring. This chart cross-references every major system for US sizes 3 to 13, with a live lookup below. A US size 6 is a UK L, an EU 52, and a Japanese 11 — 16.5 mm across, 51.8 mm around.
The chart: every system, side by side
Find your size in any column and read across. The EU column is the most literal system in the world: the size is the inner circumference in millimetres.
| US / Canada | UK / Australia | EU / ISO | Japan | Diameter (mm) | Circumference (mm) |
|---|---|---|---|---|---|
| 3 | F | 44 | 4 | 14.1 | 44.3 |
| 3.5 | G | 46 | — | 14.5 | 45.6 |
| 4 | H | 47 | 7 | 14.9 | 46.8 |
| 4.5 | I | 48 | 8 | 15.3 | 48.1 |
| 5 | J | 49 | 9 | 15.7 | 49.3 |
| 5.5 | K | 51 | 10 | 16.1 | 50.6 |
| 6 | L | 52 | 11 | 16.5 | 51.8 |
| 6.5 | M | 53 | 13 | 16.9 | 53.1 |
| 7 | N | 54 | 14 | 17.3 | 54.3 |
| 7.5 | O | 56 | 15 | 17.7 | 55.6 |
| 8 | P | 57 | 16 | 18.1 | 56.9 |
| 8.5 | Q | 58 | 17 | 18.5 | 58.1 |
| 9 | R | 60 | 18 | 19.0 | 59.7 |
| 9.5 | S | 61 | 19 | 19.4 | 60.9 |
| 10 | T | 62 | 20 | 19.8 | 62.2 |
| 10.5 | U | 64 | 22 | 20.2 | 63.5 |
| 11 | V | 65 | 23 | 20.6 | 64.7 |
| 11.5 | W | 66 | 24 | 21.0 | 66.0 |
| 12 | X | 67 | 25 | 21.4 | 67.2 |
| 12.5 | Y | 69 | 26 | 21.8 | 68.5 |
| 13 | Z½ | 70 | 27 | 22.2 | 69.7 |
The three rules of measuring at home
- Measure at the end of the day. Fingers are smallest in the morning and swell through the day — an evening measurement at room temperature is the honest one. Never measure right after exercise, in the cold, or after a salty meal.
- The paper-strip method works. Wrap a thin strip of paper (about 5 mm wide) around the base of the finger, mark where it overlaps, lay it flat, and measure in millimetres. That number is your circumference — match it to the chart. About 1.3 mm of circumference is a whole half size, so measure carefully: a sloppy wrap is the difference between a 6 and a 6.5.
- Wide bands run tight. A band wider than about 6 mm covers more skin and feels a half size smaller — size up half a step for wide bands, and consider sizing down a touch for very slim bands. Also remember your dominant hand usually runs a half size larger, and a thumb is two to three sizes bigger than the ring finger.
Output · formula · meaning
| Output | Formula | What it means |
|---|---|---|
| UK / EU / Japan size | chart lookup | Your size translated: US 6 → UK L, EU 52, Japan 11. |
| Inner diameter | circumference ÷ π | The across-the-middle measurement: 16.5 mm for a US 6. |
| Inner circumference | π × diameter | The master measurement every system is built on: 51.8 mm for a US 6. |
| Nearest size from mm | closest chart row | Measured 54.3 mm? That’s a US 7 — the lookup snaps to the nearest row. |
Who uses this
- Online ring shoppers: the listing says “54” and you wear a 7 — the chart says buy it.
- Surprise proposers: you measured her finger at 51.8 mm with a paper strip at midnight — that’s a US 6, and now you know the UK size for the London jeweler too.
- International buyers: Japanese and European jewelers don’t speak US sizes — translate before you order, not after it arrives.
- Crafters & resellers: listing a ring in all four systems doubles the buyers who can confidently click buy.
Accuracy & limitations
The US column follows the standard published US scale and the millimetre columns follow ISO 8653 (inner circumference). Two honest caveats. First, UK half-letter conventions vary between jewelers — some charts write a US 4 as H and others as H½, so treat the UK column as accurate within half a letter and confirm with the seller for fitted bands. Second, Japanese sizes vary slightly by manufacturer, and some Asian markets use their own numbering on top of the Japanese scale. Fingers themselves change roughly half a size through the day with temperature and salt, so a home measurement is a strong estimate, not a jeweler’s gauge. For an engagement ring or any size you can’t easily change, confirm with a local jeweler’s ring gauge before ordering.
Cite this calculatorBright Side Kit. “Ring Size Conversion Chart.” brightoolbox.com, 2026.
Bright Side Kit. "Ring Size Conversion Chart." https://brightoolbox.com/ring-size-chart/ Accessed October 22, 2026.Frequently asked questions
What is a US size 7 ring in millimeters?
A US size 7 ring measures 17.3 mm across the inside (diameter) and 54.3 mm around the inside (circumference). That’s a UK N, an EU 54, and a Japanese 14.
What is a US size 6 in UK ring size?
UK L. A US 6 also converts to EU 52 and Japanese 11, with a 16.5 mm inner diameter and 51.8 mm inner circumference.
Why do ring sizes differ by country?
Every country invented its own scale for the same physical measurement — the ring’s inner circumference. The US uses numbers, the UK uses letters, much of Europe just uses the circumference in millimetres (the most logical system), and Japan uses its own numbers roughly equal to circumference minus 40. The chart above translates between all of them.
What are the average ring sizes for women and men?
In the US, the average is around size 6 for women (51.9 mm around) and size 9 to 10 for men (59.5 to 62.1 mm around). Averages shift with body size and finger — the thumb runs two to three sizes larger than the ring finger.
How do I measure my ring size at home without a sizer?
Use the paper-strip method: wrap a thin strip of paper around the base of the finger, mark the overlap, lay it flat, and measure in millimetres. Match the circumference to the chart above. Measure in the evening at room temperature — fingers shrink in the cold and swell after exercise — and remember about 1.3 mm is a whole half size, so measure carefully.