Ring Size Converter — US, UK, EU & International Sizes

Shopping for a ring online? Convert sizes between US, UK, EU, and Japan standards plus diameter and circumference in millimeters — with a printable at-home measuring guide. Free.

Convert ring sizes between US, UK, EU (ISO), and Japanese systems — or from exact millimeter measurements — and get every equivalent instantly, plus a printable at-home measuring guide.

I know my size in

Size value

At-home measuring guide

No jeweler nearby? Print the guide below: a millimeter strip to wrap around your finger plus true-size ring circles to match an existing ring.

Preview: measuring strip (mm)

Cut along the strip, wrap it snugly around the base of your finger, and mark where the end overlaps — then read the millimeter length and convert it above using “Inside circumference (mm)”.

Preview: ring circles (true inner diameter)

Place an existing ring over the circles and find the one that matches the inside edge of the band.

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Everything runs in your browser. No uploads, no tracking, no data leaves your device.

No signup

Convert as many sizes as you like — no account or email required.

Free forever

Full conversion chart, mm lookup, and the printable measuring guide at no cost.

How to use it

1
Pick your size system
Choose the system you already know — US numeric, UK letters, EU/ISO, Japanese, or an exact mm measurement.
2
Enter the value
Type your size (halves like 6.5 work for US; letters like M for UK) and hit Convert.
3
Get every equivalent
See your size in all six systems at once, highlighted in the full chart below — and print the guide to measure at home.

Complete ring size chart

US / CA	UK / AU	EU (ISO)	Japan	Inside diameter	Inside circumference

EU (ISO) is the inner circumference rounded to the nearest whole millimeter. Japanese sizes run 1–27. Figures compiled from the published international ring-size conversion chart (Wikipedia).

Measuring tips that actually work

Measure at the end of the day

Fingers swell slightly as the day goes on — an evening measurement gives the most comfortable everyday fit.

Mind the knuckle

The ring must slide over your knuckle. If yours is much larger than the finger base, measure the knuckle too and pick a size between the two.

Wide bands size up

For bands wider than about 6 mm, consider going up half a US size — wide rings fit more snugly than thin ones.

Keep it warm, keep it snug

Cold fingers shrink. Measure at room temperature, and pull the strip snug but not tight — it should slide off with a little resistance.

Measure 2–3 times

Repeat the strip measurement a few times and average the readings. If you fall between sizes, most people prefer the larger one.

Charts can differ slightly

Manufacturers round half sizes differently, so allow about half a US size of tolerance when ordering from abroad.

Frequently asked questions

Which ring size system is used in the United States?

US jewelers use the numeric system shown here (3 through 13, with half sizes). If you are buying from a US store, the US number is the one to give them — everything else on this page converts to it.

How do I measure my ring size at home without a ring sizer?

Use the printable strip above: cut it out, wrap it snugly around the base of your finger, mark where the end overlaps, and read the length in millimeters. Enter that number as “Inside circumference (mm)” in the converter. Alternatively, match an existing well-fitting ring to the printed circles.

What if my measurement falls between two sizes?

Pick the larger of the two — a slightly loose ring is far more comfortable than one that pinches. For wide bands (over about 6 mm), also consider going up half a US size.

Why do different charts show slightly different conversions?

Half sizes and rounding are handled differently by different manufacturers, and UK letters do not map to mm with perfect regularity. This chart follows the published international conversion standard; allow roughly half a US size of tolerance, especially when ordering internationally.

Are quarter sizes real?

Quarter sizes exist but are rare — most jewelers stock whole and half US sizes. If a chart gives you a quarter size, round to the nearest half and check the fit guidance above.

Should the ring size differ for my dominant hand?

Usually yes — the dominant hand’s fingers run slightly larger. Measure the exact finger the ring will be worn on, not a matching finger on the other hand.

Will the printed circles be the right size?

Yes, as long as you print at 100% scale (choose “Actual size”, not “Fit to page”, in the print dialog). Before measuring, verify the printed ruler: the 0–120 mm span must measure exactly 120 mm with a real ruler.

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Ring Measuring Guide — print at 100% (Actual Size)

syedwaleed.com/ring-size-converter | Verify accuracy: the strip below must measure exactly 120 mm with a ruler.

Strip method: cut along the strip, wrap it snugly around the base of your finger, mark where the end overlaps, then read the millimeter length = your inner circumference.

Ring circles — match the inside edge of an existing ring

Tips: measure at the end of the day at room temperature; the ring must clear your knuckle; wide bands (over ~6 mm) usually need half a US size up; if between sizes, most people prefer the larger one.