Ring Size Converter
US, UK, EU (ISO 8653) & Japanese sizes — from your measurement, or from any standard size back to millimeters.
US sizes go in half steps (6, 6.5, 7 …). UK uses letters F–Z (brands vary by ±½ letter — see FAQ).
Your size
| Circumference | – |
| Inside diameter | – |
Full conversion chart
US 3–13 in half sizes, cross-referenced to UK, EU, Japan, circumference and diameter.
| US | UK | EU | JP | Circ. (mm) | Dia. (mm) |
|---|
How to measure at home
- Cut a thin strip of paper about 10 cm long (or use a soft measuring tape).
- Wrap it snugly around the base of the finger where the ring will sit — not too tight, not loose.
- Mark where the strip overlaps, then lay it flat and measure the length in millimeters. That is your circumference.
- Enter it above (use cm if your ruler reads centimeters — the converter handles cm to ring size directly).
- Measure in the evening and when your hands are warm; fingers shrink in the cold.
Frequently asked questions
What is my ring size if my finger measures 52 mm around?
52 mm is a US size 6, UK size L, EU 52 and Japanese size 12. The inside diameter is about 16.55 mm.
What is a US size 7 in millimeters?
A US size 7 ring has an inside circumference of 54.4 mm and an inside diameter of 17.32 mm. That converts to UK size N, EU 54 and Japanese size 14.
How do I convert cm to ring size?
Multiply centimeters by 10 to get millimeters, then match the circumference. For example, 5.19 cm equals 51.9 mm, which is a US size 6. This converter accepts cm directly, so you can type your cm measurement as-is.
What is US size 6 in UK, EU and Japanese sizes?
US size 6 converts to UK size L, EU 52 and Japanese size 12. Its inside circumference is 51.9 mm (2.042 inches) and its inside diameter is 16.51 mm.
What does EU ring size 52 mean?
Under ISO 8653, the EU size number is simply the inside circumference of the ring in whole millimeters. EU 52 therefore means a 52 mm inner circumference, which matches a US size 6.
How are Japanese ring sizes defined?
Japanese sizes advance by one third of a millimeter of inside diameter per size, starting at 13 mm for size 1. Size 12 has an inside diameter of about 16.67 mm, matching a US size 6.
How do I measure my ring size at home without a ring sizer?
Wrap a thin strip of paper around the base of your finger, mark the overlap, lay it flat and measure the length in millimeters. Enter that circumference above. Measure in the evening when your fingers are warm for the most reliable result.
What if my measurement falls between two sizes?
The converter shows the nearest size, how many millimeters you are off, and the half-size neighbors on both sides. Most jewelers suggest trying the larger half size first, especially for wide bands that fit more snugly.
Why do different ring size charts disagree by half a size?
There is no single worldwide manufacturing standard, so brands round the conversions slightly differently — UK letters in particular can shift by half a letter between charts. A half-size difference is normal; confirm with the jeweler before ordering an expensive ring.
Do UK ring sizes come in half sizes?
Some charts list half letters such as L 1/2, while others only use whole letters. This converter shows the nearest whole UK letter and flags the half-size tolerance, so treat neighboring letters as equally plausible.
What are the most common ring sizes for women and men?
The most commonly worn sizes are around US 6 for women and US 10 for men. A US 6 has an inside diameter of about 16.51 mm; a US 10 about 19.76 mm.
Can I convert from the diameter of a ring I already own?
Yes. Measure the inside diameter straight across the ring in millimeters (or inches) and choose diameter as the input type. The converter turns it into a circumference internally and returns all four size systems.
What is a 60 mm finger circumference in ring sizes?
60 mm converts to US size 9, UK size R, EU 60 and Japanese size 19, with an inside diameter of about 19.1 mm.
Is this ring size converter accurate?
The conversions follow the published US, UK, EU (ISO 8653) and Japanese sizing formulas, spot-checked against jeweler charts. Finger measurement itself is the biggest source of error — a paper strip can easily be off by half a size — so use the result as a strong starting point, not a guarantee.
Free tool by NRTechStudio