Ring Size Calculator (US / UK / EU / JP) — Measure at Home

Buying rings online is guessing unless you know your size. The calculator below turns one millimetre measurement into US, UK, EU and JP sizes. 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 the stainless pieces we make, see our 316L vs 304 guide.)

Prefer to cut a physical gauge?

Download the printable ring-size gauge (SVG). Print it at 100%, cut out the ring, and drop an existing ring on it — the matching size is the one that lets your ring sit inside without forcing. US sizes 4 to 12 are drawn to their real inner diameter, so the fit is physical, not arithmetic.

How to measure at home (no tools)

1. 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.
2. Existing ring method. Measure the inner diameter of a ring that already fits that finger, in millimetres, and switch the calculator to "inner diameter".
3. 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.

Ring size conversion table

UK letters and EU/JP numbers are not evenly spaced against US sizes — that is why the calculator interpolates between real anchor points instead of applying one formula.

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](https://cnszfsc.com/know-how/5-stainless-steel-jewelry-styles-for-oem-wholesale/) &amp; organizer factory.</p>
</div>

Prefer a link instead of the full tool? Point readers to https://cnszfsc.com/know-how/ring-size-calculator/.

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Next: Bracelet & Necklace Size Calculator — Measure Your Wrist or Neck →

Everything free is on one page: the free jewelry resources hub collects every chart, calculator and template above in one list.

What this means for your order

If you are still deciding, one thing decides this for you: which method you are giving the customer - circumference or inside diameter - because the two need different conversion tables and mixing them produces a size off by a whole band. Everything else on a quote page is presentation.

Where this falls short useless if the conversion is still done by guesswork at the checkout; the tool only pays when it is wired into something.

What to send us Tell us how you handle sizing enquiries today and we will tell you what setting this up changes.