Ring size chart

The full ring size chart

Ring sizes are a measurement of the finger, not of the ring’s outside. Every system below describes the same two numbers — the inside diameter and the inside circumference of the band — just with a different label on them. Once you know either measurement in millimetres, every size in the world follows from it.

The step between two whole US sizes is 2.55 mm of circumference. A half size is 1.28 mm and a quarter size is 0.64 mm — about the thickness of two sheets of paper. That is why a chart that printed a few per cent small will send you the wrong ring.

Ring size in mm: diameter or circumference?

Both are used, and mixing them up is the single most common ring-sizing mistake. Diameter is straight across the inside of the band; circumference is the way round the inside. Circumference is diameter × π, so a ring that measures 17.3 mm across is 54.4 mm round.

If someone gives you a bare number: anything between about 13 and 23 is a diameter, anything between about 41 and 76 is a circumference. European and ISO sizes are the circumference itself — ISO 54 is a ring 54 mm round.

The most common sizes

Jewellers stock a narrow band of sizes because most fingers land in it. For women that is roughly US 5 to 7, with 6 ordered most often; for men roughly US 8 to 10.5, with 9 ordered most often. Those are stocking ranges reported across the trade, not a measurement of anyone’s hand — see average ring size for what they do and do not tell you.

Every row is computed from the written definition of each system — see the notes under the full chart.

How to measure your ring size

There are four ways, in order of how well they work at home. Each has its own page with the steps:

• [Print a paper ring sizer](go:printable) — the closest thing to the steel sizer in a shop, as long as the print comes out at 100 %. The PDF has a 50 mm ruler and a bank-card outline on every sheet so you can check.
• [Measure with string or a strip of paper](go:measure) — nothing to print. Wrap, mark, measure the length with a ruler, type it in above.
• [Measure a ring you own on the screen](go:onscreen) — calibrate the screen with a bank card, then match a circle to the inside of the ring.
• [Convert a size you already know](go:conversion) — you have a UK letter or a Japanese 号 and need the US size, or the other way round.

Reading the chart without getting it wrong

• Measure at the end of the day, when fingers are at their largest. A finger measured first thing in the morning can read a full half size smaller.
• Cold hands read small, hot hands read large. A ring measured in winter outdoors will be loose in August.
• The ring has to pass the knuckle. If your knuckle is much wider than the base of the finger, size for the knuckle and accept that the ring will spin a little, or ask for sizing beads.
• Wide bands fit tighter. For a band 6 mm or wider, go up half a size; from 4 mm, a quarter.
• Buying as a surprise? Take a ring she already wears on the same finger of the same hand — the fingers of the two hands differ, often by half a size.

Questions people ask

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