Ring Size Conversion Chart: US, UK, EU and Japan Sizes

If you already know your ring size in one country's system, converting it to another is a lookup, not a guess. The table below covers US, UK/Australia, EU and Japan/Asia sizes side by side, along with the millimeter diameter and circumference each size actually corresponds to. If you don't yet know your size in any system and need to measure it first, see our full ring sizing guide for the at-home string and paper methods; this page is purely the conversion reference. To learn which part of the band gets resized, see the parts of a ring.

US to UK to EU Ring Size Conversion Chart

The table below converts US ring sizes to UK/Australia, EU and Japan/Asia equivalents, along with the inner diameter and circumference in millimeters that every system is ultimately based on. Figures are compiled from ISO 8653 ring sizing standards and cross-checked against international jewelry sizing references.

Sources: diameter and circumference figures compiled from ISO 8653 international ring sizing standard data (via the ring size reference on Wikipedia) and cross-checked against published US-UK-EU jewelry conversion tables. EU sizes follow the common jewelry-trade convention of inner circumference in millimeters, rounded to the nearest half unit; UK half sizes are shown where the closest match falls between two letters.

How to Read This Chart

Every ring size system is a label for the same underlying measurement: the ring's inner circumference in millimeters. The US and Canada use a numbered scale (whole and half sizes from about 3 to 13), the UK, Australia, Ireland and South Africa use a letter scale (A through Z, then Z½ and beyond for larger sizes), and most of continental Europe sizes rings by the circumference measurement itself, in millimeters. That's why the chart above can move between any two columns directly: if you know your size in one system, find that row, and read across.

Diameter and circumference are related by a simple formula (circumference = diameter × pi), so if a jeweler gives you one measurement you can always derive the other. In practice, circumference is the more commonly quoted number because it's what a ring sizer or a strip of paper wrapped around the finger actually measures directly.

What to Do If You're Between Two Sizes

If your measurement falls between two rows on the chart, size up rather than down, particularly for wider bands. A wider band sits more snugly against the finger than a thin band at the same numeric size, since more metal surface contacts more skin, so a wide stacking ring or statement band often needs a half size larger than a thin band would at the same measured circumference. Fingers also swell slightly in heat and shrink slightly in cold, so a size that's comfortable on a cool morning may feel tight by a warm afternoon; splitting the difference by rounding up avoids that problem more often than rounding down does. If a ring you already own is slightly too big, our ring size adjuster guide explains the inserts that take up the gap.

Don't Know Your Size in Any System Yet

If you haven't measured your ring size at all, converting between systems isn't the step you need yet, measuring is. Our separate ring sizing guide covers the at-home string and paper methods for finding your measurement from scratch; come back to this chart once you have a number or letter to convert. If sizing precisely feels like more hassle than it's worth for a gift or a first purchase, an adjustable ring sidesteps the guesswork entirely by flexing across a small range of sizes instead of locking to one.

A ring that leaves deep marks may be too snug; see ring marks on the finger.

Frequently Asked Questions

What is a size 7 ring equivalent to?

A US size 7 ring is equivalent to a UK size N½, a EU size 54, and roughly a 17.3mm inner diameter or 54.4mm inner circumference. It's one of the most common ring sizes for women in the US (see the average ring size for women for what the numbers do and do not tell you).

How do I calculate my ring size?

Measure the inner circumference of a ring that already fits, or wrap a strip of paper or string around your finger and measure the length in millimeters, then match that number to the circumference column on a conversion chart. Our full ring sizing guide walks through both methods step by step.

What size ring should I get if my finger measures 2.5 inches around?

A 2.5 inch finger circumference converts to about 63.5mm, which corresponds to roughly a US size 10.5, UK U½, or EU 63.5. Convert inches to millimeters first (inches × 25.4) before matching to a sizing chart, since most charts are built in millimeters.

Is a US size 8 ring considered big?

A US size 8 is a moderately large women's ring size and a smaller-to-average men's size; it corresponds to roughly an 18.1mm diameter. It's common enough that most jewelers stock it as a standard size, not a special order.

Are ring size conversions exact across every country?

Ring size conversions are close but not always perfectly exact, because a few countries round their scales slightly differently even though all of them are based on the same millimeter measurement. For a purchase that matters, matching by the millimeter diameter or circumference directly, rather than by the size label alone, is the most reliable approach.

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