Japanese Ring Sizes and International Conversions

Japan uses its own ring sizes, numbered from 1 upwards. Each step adds about one millimetre to the inner circumference, which makes the system simple to convert once you know the starting point: Japanese size 1 is about 41 millimetres around the inside.

Conversion chart

Japan Circumference (mm) Diameter (mm) US UK Europe
4 44 14.0 3 F 44
7 47 15.0 4 H½ 47
9 49 15.6 5 J½ 49
12 52 16.6 6 L½ 52
14 54 17.2 7 N½ 54
17 57 18.1 8 P½ 57
19 to 20 59 to 60 19.0 9 R½ 60
22 62 19.7 10 T½ 62
24 to 25 64 to 65 20.5 11 V½ 65
27 67 21.3 12 Y 67

The conversions are approximate. Half sizes and differences between makers mean that a ring may fit slightly differently from the chart.

How maisons size their rings

Many European jewellery houses mark their rings with the European size, which is simply the inner circumference in millimetres. A ring marked 52, for example, is about Japanese size 12 or US size 6. Wide bands fit more tightly than narrow ones of the same size, so many people choose a size up for bands wider than about six millimetres.

Measuring at home

  • Wrap a thin strip of paper around the base of your finger, mark where it overlaps and measure the length in millimetres. That is your circumference.
  • Or measure the inside diameter of a ring that fits you well, edge to edge, and use the chart.
  • Measure at the end of the day, when fingers are slightly larger, and avoid measuring when cold.
  • Make sure the ring will pass over your knuckle.

Resizing

Many gold and platinum rings can be resized by a jeweller, but some cannot: eternity rings, rings with engraving or patterns all the way round, and certain designer pieces. Resizing can also affect a maison's service record. Our descriptions give the size of each ring, and our curator desk can advise before you buy.

Related references

Submit Your Case File

Every bespoke partnership begins with clarity. Tell us what you seek, what inspired you, and the boundaries of your project.


What Happens After You Submit

Your Case File is reviewed personally by a senior advisor. We examine your objectives, logistics requirements, cultural considerations, and practical constraints. You will receive a tailored proposal outlining recommended services, timelines, and all applicable fees.

  • Bespoke service design tailored to your specific needs
  • Museum-grade logistics for art, antiques, fashion, and collectibles
  • Transparent partnership with no hidden or surprise costs

“All fees, deposits, and retainers will be clearly presented for approval before any work begins.”

Your Case File

Please complete the form carefully. The more precise your information, the more accurately we can prepare your assessment.

All fields are required to submit this form.

Kindly allow us a brief moment to review your submission. A senior advisor will be in touch with your personalised next steps.

Thank you for entrusting us with your vision. We look forward to representing you with precision and discretion.