Buying rings online is guessing unless you know your size. This free ring size calculator turns a simple measurement into US, UK, EU and JP sizes in seconds — no jeweller, no printable chart required. It is built for the way people actually measure at home: wrap a strip of paper around the finger, read the length in millimetres, type it in. (For stainless pieces we make, see our 316L vs 304 guide.)
Download printable ring-size strip (SVG)
Ring size conversion table
| US | UK | EU | JP | Circumference (mm) | Diameter (mm) |
|---|---|---|---|---|---|
| 4 | H ½ | 47 | 7 | 46.8 | 14.9 |
| 5 | J ½ | 49 | 9 | 49.3 | 15.7 |
| 6 | M | 52 | 12 | 51.9 | 16.5 |
| 7 | N ½ | 54 | 14 | 54.4 | 17.3 |
| 8 | P | 57 | 16 | 57.0 | 18.1 |
| 9 | R ½ | 59 | 18 | 59.5 | 18.9 |
| 10 | T ½ | 62 | 20 | 62.1 | 19.8 |
| 11 | V ½ | 64 | 23 | 64.6 | 20.6 |
| 12 | Y | 67 | 25 | 67.2 | 21.4 |
How to measure at home (no tools)
- String or paper strip method. Cut a strip ~2 mm wide and 100 mm long. Wrap it snugly around the base of the finger you will wear the ring on, mark where it overlaps, then measure that length in millimetres — that is your circumference. Type it into the calculator above.
- Existing ring method. Measure the inner diameter of a ring that already fits that finger, in millimetres, and enter it as diameter.
- Measure when warm. Fingers swell in heat and shrink when cold; measure at room temperature, ideally end of day. If you are between sizes, size up by half.
FAQ
Which finger should I measure? The one you will wear the ring on — index, middle and ring fingers differ by several sizes.
Why do US and UK sizes differ? They use different scales (US numeric, UK letters). The calculator converts both from the same millimetre measurement, so either is reliable.
Does this work for stainless steel rings? Yes — sizing is the same for any metal. Our care guide covers keeping the finish bright after you know the size.
Related: full ring size conversion chart, the 316L vs 304 explainer, and our jewelry organizer line for storage once the ring arrives.
Embed this ring size calculator on your site
Free to embed on any blog, shop or how-to page. Copy the code below and paste it into your HTML; keep the credit link so your readers can find the source. Questions about stainless steel ring sizing? see our care guide.
<div> <iframe src="https://cnszfsc.com/know-how/ring-size-calculator/" width="100%" height="560" frameborder="0" style="border:1px solid #d8d5cc;border-radius:8px;"></iframe> <p style="font-size:12px;color:#777;">Ring size calculator by <a href="https://cnszfsc.com/" rel="dofollow">FSC CRAFT</a> — stainless steel jewelry & organizer factory.</p> </div>
Prefer a link instead of the full tool? Point readers to https://cnszfsc.com/know-how/ring-size-calculator/.
