Ring Size Chart: US, UK/AU, EU & MM Conversion

Ring Size Chart (US, UK/AU, EU & MM)

Here's the master conversion chart. Find the size you already know, then read across the row for its equivalent everywhere else. The inside diameter and circumference are the physical measurements every system is built on — when in doubt, go by the millimetres.

The chart gives every size in mm and inches (for cm, just divide the mm by 10). Half sizes fall neatly between these rows — a US 9.5 sits between the 9 and 10. Australia and New Zealand share the UK letter system exactly, so the UK/AU column covers all three. Letters are the closest match; for a precise fit, use the diameter or circumference in millimetres.

Men's Ring Size Chart

Men's and women's rings use the exact same scale — a US 9 is a US 9 on anyone. The only real difference is where most people land. The average men's ring size is a US 9 to 10 (UK/AU R½ to T½), with most men falling between a US 8 and 12. For reference, women most commonly sit at a US 6 to 7.

If you're buying a men's ring as a surprise, a US 10 is the safest single guess — but a borrowed ring measured on the chart beats a guess every time. Browse the rings and wider men's jewellery range once you know the number.

How to Measure Your Ring Size at Home

You don't need a jeweller to get a reliable size. Two methods work well:

The string or paper method

Wrap a strip of paper, string or dental floss snugly around the base of the finger — not tight, not loose. Mark where it overlaps, then lay it flat and measure the length in millimetres. That length is your inside circumference; find it in the chart above to get your size. Measure two or three times and take the average, since paper can stretch or absorb moisture.

Measure a ring that already fits

Even more accurate: take a ring that fits the right finger, and measure the distance straight across the inside with a ruler in millimetres. That's your inside diameter — match it to the chart. This is the trick for sizing a surprise gift without asking.

When to measure

Fingers change through the day, so measure in the late afternoon or evening when they're warm and at their largest. Avoid measuring when you're cold or straight after exercise — fingers can shrink up to half a size, and you'll end up with a ring that spins in winter. Always measure the exact finger and hand the ring will live on; your dominant hand usually runs about half a size larger. For an expensive ring, it's worth confirming with a professional — GIA recommends having fine jewellery sized and checked by a qualified jeweller.

Printable and On-Screen Sizing

Want to measure without any maths? A printable sizer is the easiest route — but accuracy depends entirely on the print scale. Print the guide at 100% (no "fit to page"), then check it with a ruler: the reference line should measure exactly what it says, or a credit card laid on the printout should be 85.6mm wide. If that's off, every reading will be off too.

Be wary of "actual size" charts you view directly on a phone or laptop — screens vary in pixel density, so an on-screen ring is only true-size if the page lets you calibrate it against a bank card first. When in doubt, the string method and the millimetre chart above never depend on a screen. For a ready-made printable version, use our ring sizing guide.

How the Sizing Systems Differ

Every region built its own system before the world started shopping across borders, which is why the labels don't line up:

• US & Canada use a number scale (roughly 3 to 13, in quarter steps). Each whole size adds about 0.8mm of inside diameter, or 2.55mm of circumference.
• UK, Australia & New Zealand use letters, A to Z with half sizes. Australia and the UK share the identical scale, so any UK chart works in Australia.
• Europe keeps it simplest: the size is the inside circumference in millimetres. A size 54 ring measures 54mm around inside.

That European approach is the international standard, ISO 8653:2016, which defines a ring size as its inner circumference in millimetres. It's why the millimetre columns in the chart are the ones to trust when you're converting between countries — the letters and numbers are just regional names for the same physical measurement.

Getting the Fit Right

The chart gets you the number; a few habits get you the fit.

• Between two sizes? Size up. A slightly loose ring is more comfortable than one that won't pass your knuckle, and a jeweller can size a plain band down more easily than up — Jewelers of America explains how resizing works.
• Wide bands run tight. A chunky band covers more of your finger, so for anything over about 4mm wide, go up half a size.
• Account for the day. Temperature, heat, salt and hydration all move your size by up to half a size — build in a little margin rather than sizing to your smallest reading.
• Thumbs are bigger. A thumb usually runs two to three sizes larger than a ring finger, so never assume they match.

Frequently Asked Questions