Standard Japan ring sizing reference
Japan uses a simple ascending numeric scale, typically running from around size 1 up to size 30, where the number climbs in step with the ring's inside circumference — there's no letters or half-sizes to navigate, just a straightforward number that gets larger as the ring does.
This same style of numeric scale, or something very close to it, is commonly used across other parts of Asia as well, though exact reference points can vary slightly by country and even by individual jeweler, so it's worth confirming locally for anything outside Japan itself.
Each Japan size below is matched to its inside diameter, inside circumference, and closest US equivalent.
| Japan Size | US Equivalent | Inside Diameter | Inside Circumference |
|---|---|---|---|
| Size 4 | US 3 | 14.1 mm | 44.2 mm |
| Size 5 | US 3.5 | 14.5 mm | 45.5 mm |
| Size 7 | US 4 | 14.9 mm | 46.8 mm |
| Size 8 | US 4.5 | 15.3 mm | 48.0 mm |
| Size 9 | US 5 | 15.7 mm | 49.3 mm |
| Size 10 | US 5.5 | 16.1 mm | 50.6 mm |
| Size 12 | US 6 | 16.5 mm | 51.9 mm |
| Size 13 | US 6.5 | 16.9 mm | 53.1 mm |
| Size 14 | US 7 | 17.3 mm | 54.4 mm |
| Size 15 | US 7.5 | 17.7 mm | 55.7 mm |
| Size 17 | US 8 | 18.1 mm | 57.0 mm |
| Size 18 | US 8.5 | 18.5 mm | 58.3 mm |
| Size 19 | US 9 | 18.9 mm | 59.5 mm |
| Size 20 | US 9.5 | 19.3 mm | 60.8 mm |
| Size 22 | US 10 | 19.7 mm | 62.1 mm |
| Size 23 | US 10.5 | 20.1 mm | 63.4 mm |
| Size 24 | US 11 | 20.5 mm | 64.6 mm |
| Size 26 | US 11.5 | 20.9 mm | 65.9 mm |
| Size 27 | US 12 | 21.3 mm | 67.2 mm |
| Size 28 | US 12.5 | 21.7 mm | 68.5 mm |
| Size 29 | US 13 | 22.1 mm | 69.7 mm |
Need US, UK, or EU sizing instead?
Open the converterQuick reference: Japan size 9 = US 5, Japan size 14 = US 7, Japan size 19 = US 9, Japan size 22 = US 10 — the full Japan-to-US breakdown for every size is in the chart above.
For every home method in one place, including common mistakes to avoid, see our complete measuring guide.
China's ring sizing commonly aligns closely with Japan's numeric scale, and it's widely used as a practical reference across the region, but it isn't universally identical everywhere — some retailers use their own local reference points. If you're buying from a jeweler outside Japan, it's worth double-checking which exact scale they mean by "size," especially for a purchase you can't easily resize.
Wider bands (roughly 6mm and up) tend to sit more snugly than a thin band at the same labeled size, so it's common to size up a step or two for a wide band — our guide to sizing for wide bands covers exactly how much. If you're between sizes, sizing up is usually the safer choice, since a slightly loose ring can be resized smaller more easily than a tight one can be resized larger.
Sizing a ring as a surprise? Our engagement ring sizing guide covers how to get a discreet, reliable estimate without asking directly.
Match your Japan size against the chart above — both systems are cross-referenced against the same inside circumference, so the conversion is exact rather than approximate. Our converter does this instantly, or see our full US Ring Size Chart.
A US size 7 is Japan size 14 — both describe the same 54.4mm inside circumference, just on different numbering scales. Use the chart above to convert any other US size to its Japan equivalent.
No — Japan and the US use completely different numeric scales, so the size numbers themselves don't match. They do measure the exact same thing (inside circumference), so any US size has a precise Japan equivalent — a US 7 is a Japan 14, for example — it's just labeled differently.
They're closely aligned and Japan's scale is commonly used as a practical reference across China and other parts of Asia, but it isn't universally identical — some retailers use their own local reference points, so it's worth confirming with the specific jeweler for anything hard to resize.
Japan size 15 is equivalent to US 7.5 (about 55.7mm circumference), and Japan size 11 falls between the standard chart steps at roughly US 5.5-6. Check the chart above for the closest official size, or use our converter for any Japan size.
Japan's numeric scale and the UK's letter scale both describe the same inside circumference, just labeled differently — for example, Japan size 14 matches UK size N. See our full UK Ring Size Chart for every letter's equivalent, or our world comparison chart for every system side by side.
Like most countries, Japan standardized its own numeric reference scale independently rather than adopting another country's system — the underlying measurement (inside circumference) is identical worldwide, only the labeling scale differs. That's exactly what a conversion chart or converter tool resolves.
Free ring size conversion and measurement tools for US, UK, Japan, and international sizing systems.
© Rings Sizer. Sizes are estimates — confirm in person for a permanent purchase.