Ring Size Converter
Convert between US, UK, EU, and mm ring sizes instantly
Find your ring size in any system — US/Canada, UK/Australia, EU/Germany, or finger circumference and diameter in mm. Perfect for ordering rings online from international jewellers.
What Are Ring Size Systems?
Ring sizing is not universal — different countries use completely different systems to describe the same physical ring size. The three major systems are the US/Canada numerical system, the UK/Australia alphabetical system, and the EU/German circumference-in-mm system. This makes international ring buying confusing without a conversion tool.
All systems ultimately measure the same thing: the inner circumference or diameter of a ring. The US system uses numbers from 3 to 13 (with half sizes), the UK system uses letters A to Z (with half sizes like N½), and the EU system uses the inner circumference in millimetres (typically 44–70 mm for adult rings).
India uses a system similar in range to the US but with slightly different numbering. Japan uses numbers 1–27 based on inner circumference, while Switzerland and France also use the circumference system similar to the EU but may differ by one or two units due to measurement conventions.
How to Use This Ring Size Converter
- Choose your input system — Select from US/Canada, UK/Australia, EU/Germany, Circumference (mm), or Diameter (mm) in the From System dropdown.
- Enter your ring size — For US sizes type a number (e.g. 7). For UK sizes type a letter (e.g. N). For EU sizes type the number (e.g. 54). For circumference, type the mm measurement.
- Read all equivalents — The results panel instantly shows your size in every system, including the finger circumference and diameter in millimetres.
- Use the measurement tips below if you don't know your ring size and need to measure at home before ordering.
Ring Size Conversion Reference
The relationship between the main ring size systems is based on the inner circumference (C) of the ring. EU size = inner circumference in mm. US size and UK letter are mapped to specific circumference ranges:
| US Size | UK Size | EU Size | Circumference (mm) | Diameter (mm) |
|---|---|---|---|---|
| 5 | J | 48 | 49.3 | 15.7 |
| 6 | L | 51 | 51.9 | 16.5 |
| 6.5 | M | 52 | 53.1 | 16.9 |
| 7 | N | 54 | 54.4 | 17.3 |
| 8 | P | 57 | 57.0 | 18.1 |
| 9 | R | 59 | 59.5 | 18.9 |
| 10 | T | 62 | 62.1 | 19.8 |
| 11 | V | 65 | 64.6 | 20.6 |
Common Ring Sizes by Gender
| Category | US Size | UK Size | EU Size | Circumference |
|---|---|---|---|---|
| Women — small | 5–5.5 | J–K | 48–49 | 49–51 mm |
| Women — average | 6–6.5 | L–M | 51–52 | 52–53 mm |
| Women — large | 7–8 | N–P | 54–57 | 54–57 mm |
| Men — small | 8–9 | P–R | 57–59 | 57–60 mm |
| Men — average | 9–10 | R–T | 59–62 | 60–62 mm |
| Men — large | 11–12 | V–X | 65–67 | 65–67 mm |
Worked Examples
Example 1 — US to UK and EU: You normally wear a US size 7 ring. Entering 7 in the converter shows UK size N and EU size 54, with a circumference of 54.4 mm. When ordering from a European jeweller using EU sizing, you would select size 54.
Example 2 — Measuring at home: You wrap a paper strip around your finger and it measures 57 mm. Entering 57 in the Circumference (mm) field shows US size 8, UK size P, EU size 57. This is the industry "average" for men's wedding bands.
Example 3 — Diameter to size: An existing ring measures 17.3 mm across (diameter). The circumference is 17.3 × π ≈ 54.4 mm. This matches US size 7, UK N, EU 54 — confirming the ring size before reordering.
Tips for Getting the Right Ring Size
- Measure at the end of the day — fingers swell slightly in warm weather and evenings. Measuring then ensures the ring won't be too tight.
- Measure the correct finger — the same-numbered finger on your dominant hand is often slightly larger than on the other hand.
- Use string or paper, not thread — thin thread can stretch and give inaccurate readings.
- When between sizes, go larger — it is easier to resize a ring down than up, and a slightly loose ring is more comfortable than a tight one.
- Wide bands fit tighter — if ordering a band wider than 6 mm, consider going up half a size from your measured size.
- Check brand-specific charts — some jewellers (especially Asian brands) use slightly different measurements. Always confirm with the seller's own size chart.
- Temperature matters — fingers can shrink by up to half a size in cold weather. Measure at room temperature (18–22°C) for the most reliable reading.
Frequently Asked Questions
Wrap a thin strip of paper around your finger, mark where it overlaps, and measure the length in mm — that is your finger circumference. Enter it in the Circumference (mm) field of our converter to find your size in any system.
The average ring size for women in the US is size 6 to 6.5, which corresponds to approximately UK size L–M and EU size 51–52.
The average ring size for men in the US is size 9 to 10, which corresponds to approximately UK size R–S and EU size 62–64.
US ring sizes use numbers (3–13), while UK ring sizes use letters (F–Z). Both systems are based on finger circumference but use different scales. US size 7 corresponds to UK size N and EU size 54.
Fingers are slightly larger in the evening and when warm. For the most accurate measurement, measure at the end of the day when fingers are at their largest — this ensures the ring won't be too tight.
EU ring sizes (used in Germany, France and much of Europe) are based on the inner circumference of the ring in millimetres. A size 52 ring has an inner circumference of 52 mm, which is a diameter of about 16.6 mm.
If your measurement falls between two sizes, it is generally safer to choose the larger size. Rings can often be resized smaller more easily than larger, and a ring that is slightly loose is more comfortable than one that is too tight.