Ring size chart for US, UK, EU, Japan, China and Russia

Ring sizes look like six unrelated systems. They are not. Every one of them is a label attached to the same physical fact, the inner diameter of the ring in millimetres. Once you have that number, every other column follows automatically.

If you are shopping in the common US 3–10 range, the focused women’s ring size chart adds exact-hand, engagement-band, knuckle and ordering checks to the same conversions.

The complete international ring size chart

How do you read the chart?

Each column is a different naming convention for the same underlying measurement, and knowing what each one is counting makes the whole table easier to trust.

US and Canada use numbers that may be offered in whole, half or quarter steps. Each full US size is about 0.81 mm of diameter; the increments a seller stocks vary by product and maker.

UK, Australia and Ireland use letters in half-letter steps, running from A at the small end through Z and then continuing as Z+1, Z+2 and so on for larger fingers.

EU and ISO is not really a size at all. It is the inner circumference in millimetres, which is why the numbers sit in the forties, fifties and sixties. The standard is ISO 8653:2016.

Japan uses its own integer scale, running roughly from 1 to 27.

China is often shown with a Japan-like integer scale on international charts, but sellers can use a different local table. Treat the millimetre measurement and the seller’s own chart as the authority for an order.

Russia uses the ring’s inner diameter in millimetres. Major Russian jeweller SOKOLOV explains that the size equals the inner diameter and that classic retail sizes commonly move in 0.5 mm steps. That makes a 17.3 mm diameter roughly a Russian 17.5, not 54.4. Always compare the unrounded diameter with the seller’s own increments.

What is the maths behind the chart?

If you ever want to check a chart rather than take it on trust, the relationship the industry uses for US sizes is straightforward:

Inner circumference in mm = 36.537 + 2.5535 × US size

Divide that by π to get the diameter. A US 7 gives 36.537 plus 17.875, which is 54.41 mm of circumference, and 54.41 divided by π is 17.3 mm of diameter. That is exactly what the table above says, and exactly what Ring Sizer shows in the app.

Being able to reproduce the numbers matters more than it sounds. Conversion charts on the open web disagree with each other surprisingly often, usually at the extremes of the range where different sources round differently. A chart you can derive is a chart you can check.

Convert any size instantly

Which column does your seller mean?

When you are not sure, send the millimetre diameter. It is the only unambiguous answer, any jeweller anywhere can work from it, and it removes an entire category of transcription error from the transaction.

How should you handle half sizes and rounding?

US rings may be offered in whole, half or quarter sizes depending on the seller. If a measurement lands between chart rows, keep the unrounded millimetres and repeat it before choosing either label. The nearest size is only a starting point: band width, knuckle clearance, interior profile and ordinary conditions can change which neighbour fits securely.

Use the dedicated between ring sizes guide for the size-up-or-down decision and a practical quarter-size checklist. This chart deliberately stops at conversion. Its job is to label the physical measurement accurately, not to prescribe one rounding rule for every ring. Send the seller the original millimetres whenever the result sits close to a boundary.

What can a size chart not tell you?

A chart describes a circle. It knows nothing about three things that materially change how a ring fits.

Band width. A wider band can feel different from a narrow reference at the same nominal size because it changes contact and knuckle passage. There is no universal width threshold or half-size addition. Test a gauge or sample that matches the intended width. The wide band guide explains that process.

Interior profile. A domed comfort-fit interior can feel different from a flat interior, but the effect varies with the curve, width, edge shape, maker and finger. Do not subtract a fixed quarter or half size; compare the intended profile directly.

Knuckles. If your knuckle is significantly wider than the base of your finger, the chart’s answer will not be the answer, and no amount of precision in the measurement changes that. Read the big knuckle guide before ordering.

What are the average sizes, for a sanity check?

The most commonly ordered women’s sizes cluster between a US 5½ and a US 7. Men’s cluster between a US 9 and a US 11.

That is not a rule and plenty of people sit outside it. It is a way of catching a measurement that has gone badly wrong. If your result lands well outside those bands, check the three usual suspects before ordering: that you measured the inner edge rather than the outer one, that you did not confuse circumference with diameter, and that you measured the finger the ring is actually for.

There is more detail, including where published averages come from and why sources disagree, in the average ring size guide.

Should you print this chart or use it on screen?

Either works, with one condition attached to printing.

A printed chart is only accurate if it prints at exactly one hundred percent scale, and printer drivers routinely apply “fit to page” without saying so. A two percent scale error moves every circle on the page by roughly a full ring size. If you do print it, hold a bank card against a printed reference before trusting anything on the sheet.

Using it on screen avoids that problem entirely, provided the app knows your device’s pixel density rather than assuming one. That distinction is covered in the printable ring sizer guide, which explains what goes wrong with both approaches and how to verify either in about ten seconds.