Ring Size Chart — US, UK, EU, Japan & India
The complete ring size chart: every US size from 3 to 13 in half sizes, with inner diameter and circumference in millimetres and the UK, EU, Japanese and Indian equivalents.
Reviewed & updated: November 2026 — chart re-verified against ISO 8653
Full ring size chart
| US / Canada | Diameter (mm) | Circumference (mm) | UK / Australia | EU (ISO) | Japan | India |
|---|---|---|---|---|---|---|
| 3 | 14.1 | 44.2 | F | 44 | 4 | 4 |
| 3.5 | 14.5 | 45.5 | G | 46 | 5 | 5 |
| 4 | 14.9 | 46.8 | H½ | 47 | 7 | 7 |
| 4.5 | 15.3 | 48.0 | I½ | 48 | 8 | 8 |
| 5 | 15.7 | 49.3 | J½ | 49 | 9 | 9 |
| 5.5 | 16.1 | 50.6 | K½ | 51 | 11 | 11 |
| 6 | 16.5 | 51.9 | L½ | 52 | 12 | 12 |
| 6.5 | 16.9 | 53.1 | M½ | 53 | 13 | 13 |
| 7 | 17.3 | 54.4 | N½ | 54 | 14 | 14 |
| 7.5 | 17.7 | 55.7 | O½ | 56 | 15 | 15 |
| 8 | 18.1 | 57.0 | P½ | 57 | 16 | 16 |
| 8.5 | 18.5 | 58.3 | Q½ | 58 | 18 | 18 |
| 9 | 18.9 | 59.5 | R½ | 60 | 19 | 19 |
| 9.5 | 19.4 | 60.9 | S½ | 61 | 20 | 20 |
| 10 | 19.8 | 62.1 | T½ | 62 | 21 | 21 |
| 10.5 | 20.2 | 63.4 | U½ | 63 | 22 | 22 |
| 11 | 20.6 | 64.6 | V½ | 65 | 23 | 23 |
| 11.5 | 21.0 | 66.0 | W½ | 66 | 25 | 25 |
| 12 | 21.4 | 67.2 | X½ | 67 | 26 | 26 |
| 12.5 | 21.8 | 68.5 | Y½ | 69 | 27 | 27 |
| 13 | 22.2 | 69.7 | Z½ | 70 | 29 | 29 |
Full chart, US sizes 3 to 13 in half sizes. EU size is the rounded circumference in mm. Japan and India share the same values on this chart.
For true-to-size circles, use the printable ring sizer instead — tables print fine at any scale, circles do not.
Ring size conversion at a glance
How to read the chart
Measure once, in millimetres. If you measured around your finger, find your circumference; if you measured across a ring, find your diameter. Read across the row for every country's size. Between rows? Take the larger size. New to measuring? Start with how to measure ring size, check the average ring size for a sanity check, or jump to the men's chart or women's chart.
Frequently asked questions
What is a US size 7 in mm?
How do I print this chart accurately?
How our chart is built — methodology & sources
ISO 8653:2016 — the millimetre foundation
Every number on this site starts from ISO 8653:2016, the international standard that defines a ring size by the ring’s inner circumference in millimetres. That is why the EU size is simply that circumference, rounded: a ring measuring 54.4 mm around the inside is EU 54. Diameter is circumference ÷ π, so the same ring is 17.3 mm across.
The US formula
US sizes follow the linear formula circumference (mm) = 36.5 + 2.55 × US size. Each full US size adds 2.55 mm of circumference (about 0.81 mm of diameter). Worked example: a 54.4 mm circumference gives (54.4 − 36.5) ÷ 2.55 = 7.02 — a US size 7. Our calculator uses this formula for its precise estimate, then snaps to the nearest chart row for the other systems.
BS 6820 — why UK sizes are a lookup, not a formula
UK and Australian sizes follow British Standard BS 6820: letters step by 1.25 mm of circumference, starting from size C at 40 mm. Because 1.25 mm steps do not align with the US system’s 2.55 mm steps, a US size can land between two UK half-letters — which is why UK equivalents are looked up in the chart rather than calculated, and why two honest charts can differ by half a letter.
Japan and India
Japanese and Indian sizes come from published jewellers’ conversion charts anchored to the same millimetre measurements. On our chart the two systems share values (US 7 = 14 in both), which matches the most widely published charts.
Accuracy & sources
Sources: ISO 8653:2016 (ring size definition), BS 6820 (UK letter scale), the standard US circumference formula above, and published jeweller conversion charts for Japan and India. The on-screen sizer is calibrated against the ISO/IEC 7810 bank-card width of 85.60 mm. Honest limit: charts vary by up to half a size between jewellers, and fingers change size through the day — treat any home measurement as a strong estimate, confirm in millimetres with your jeweller before buying, and double-check with a jeweller’s mandrel for engagement or non-resizable rings. This chart was reviewed and re-verified against ISO 8653 in November 2026.
Popular sizes in detail
One page per size — exact millimetres and inches, every equivalent, and who typically wears it: US 5 · US 6 · US 6.5 · US 7 · US 7.5 · US 8 · US 9 · US 10.