My proposal planning panic: A few years ago, I was preparing to propose. I secretly borrowed one of my partner's rings, pressed it into a bar of soap to make an impression, and measured the diameter with a ruler. Confident, I ordered a beautiful ring in "US size 7". It arrived, and on the big day, it wouldn't go past the knuckle. Turns out, I'd measured the inner diameter of a ring she wore on her right hand — which was a full size smaller than her left ring finger. We laughed (eventually), but I learned: ring sizing is precise, and guessing is risky. Now I use a proper converter and recommend everyone does the same.
Ring sizes are a small number with big consequences. Whether you're buying an engagement ring, a gift from abroad, or just treating yourself, knowing your exact size across different international systems is essential. Unlike shoes or clothes, rings can't be "a little loose" — they need to fit snugly over the knuckle and sit comfortably at the base. This guide covers the two main measurement methods (circumference and diameter), explains how US, UK, EU, and Japanese sizes work, and points you to a free tool that converts them all.
Enter your ring size in any system — US, UK, EU, JP, or circumference in mm — and see all equivalents immediately.
Circumference (mm) → all sizes — the most accurate method.
Diameter (mm) → all sizes — for measuring existing rings.
US, UK, EU, JP, AU, CN — every major ring system.
No signup, no ads — just precise conversion.
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Ring sizes are based on the inner circumference of the ring (in millimeters) or its inner diameter (also in mm). Most international size charts use circumference, but the US uses an arbitrary numeric scale. Here's how to measure accurately at home.
Pro tip: Fingers swell slightly in warm weather and shrink in cold. Measure at room temperature, ideally at the end of the day.
Once you have your circumference or diameter, you can convert to any country's scale. Here's how the major systems work:
US ring sizes are numbers (e.g., 6, 7, 7.5). Each whole size increases the inner circumference by about 2.5 mm. Half and quarter sizes are common.
The UK uses letters, with half sizes (e.g., L, L½, M). A UK size L is roughly a US 6. The scale is linear but offset from US numbers.
European ring sizes are simply the inner circumference in millimeters, minus 40. So a 52 mm circumference = EU size 52. (Sometimes labeled as 52, or 52.0).
Japanese and Chinese ring sizes are just the circumference in millimeters. A JP 14 is a 54 mm circumference (size 14). Simple and logical.
| Circumference (mm) | Diameter (mm) | US/CA | UK/AU | EU | JP/CN |
|---|---|---|---|---|---|
| 46.8 | 14.9 | 4 | H | 46.5 | 7 |
| 49.3 | 15.7 | 5 | J½ | 49 | 9 |
| 51.9 | 16.5 | 6 | L | 51.5 | 11 |
| 54.4 | 17.3 | 7 | N½ | 54 | 14 |
| 57.0 | 18.1 | 8 | P½ | 56.5 | 16 |
| 59.5 | 18.9 | 9 | R½ | 59 | 18 |
| 62.1 | 19.8 | 10 | T½ | 61.5 | 20 |
| 64.6 | 20.6 | 11 | V½ | 64 | 23 |
1️⃣ Go to Global Size Converter and select "Ring Sizes"
2️⃣ Enter your known measurement — circumference (mm), diameter (mm), or a size from any country
3️⃣ See US, UK, EU, JP, AU, and more instantly.
Works for men's and women's rings.
Bookmark Global Size Converter — the only ring sizing tool you'll need.
For the full international ring size converter, visit global-size-converter.vercel.app — accurate, fast, and free.
— measure smart, wear forever.