Quick Ring Size
Size chart

Ring size chart

A ring size is a millimetre measurement in disguise. Every US size maps to a fixed inner diameter and circumference, and those millimetres convert cleanly to UK letters, EU/ISO numbers, and Japan sizes. Find any measurement you have and read across.

EU/ISO is the inner circumference in millimetres, rounded. UK letters and Japan sizes are approximate. See the methodology for sources.
US / CA Diameter (mm) Diameter (in) Circumf. (mm) Circumf. (in) UK / AU EU / ISO Japan
3 14.1 0.55 44.2 1.74 F 44 4
3.5 14.5 0.57 45.4 1.79 G 45 5
4 14.9 0.59 46.7 1.84 H 47 7
4.5 15.3 0.60 48.0 1.89 I 48 8
5 15.7 0.62 49.3 1.94 J½ 49 9
5.5 16.1 0.63 50.5 1.99 K½ 51 10
6 16.5 0.65 51.8 2.04 L½ 52 12
6.5 16.9 0.67 53.1 2.09 M½ 53 13
7 17.3 0.68 54.4 2.14 N½ 54 14
7.5 17.7 0.70 55.6 2.19 O½ 56 15
8 18.1 0.71 56.9 2.24 P½ 57 16
8.5 18.5 0.73 58.2 2.29 Q¼ 58 18
9 18.9 0.75 59.5 2.34 R½ 59 19
9.5 19.4 0.76 60.7 2.39 S½ 61 20
10 19.8 0.78 62.0 2.44 T½ 62 21
10.5 20.2 0.79 63.3 2.49 U½ 63 22
11 20.6 0.81 64.6 2.54 V½ 65 24
11.5 21.0 0.83 65.8 2.59 W½ 66 25
12 21.4 0.84 67.1 2.64 X½ 67 26
12.5 21.8 0.86 68.4 2.69 Y½ 68 27
13 22.2 0.87 69.7 2.74 Z½ 70 29
13.5 22.6 0.89 70.9 2.79 Z1½ 71 30

How to read it

Start from whatever you know. If you measured across the inside of a ring, use the diameter column. If you wrapped a string around the finger, use the circumference column. Read across for the size in each country's system. The numbers grow in a straight line: each full US size adds about 0.81 mm of diameter, or 2.55 mm of circumference, which is why measuring carefully to the nearest 0.1 mm is worth the effort.

Rather than read it off a table, you can measure directly on the screen or type a millimetre measurement to get the size instantly.

Men's and women's sizes

Ring sizes aren't gendered: the same US 7 is a US 7 for anyone. Men simply tend to land higher on the chart (commonly 8 to 11) and women lower (commonly 5 to 7). For the averages and their sources, see men's average ring size and women's average ring size.

Sources

The millimetre values come from the standard linear relationship where each full US size differs by about 0.81 mm of inner diameter (2.55 mm of circumference). The EU column follows ISO 8653, where the size equals the inner circumference in millimetres. The full write-up, including where charts disagree, is on the methodology page.

Common questions

How do I read a ring size chart?

Find a known measurement and read across. If you measured a ring's inner diameter in millimeters, find that value in the diameter column and read across to your US, UK, EU, and Japanese size. If you measured your finger's circumference, use the circumference column instead. Every full US size is about 0.8 mm of diameter or 2.55 mm of circumference apart, so small measuring errors move you by a fraction of a size.

What size ring is 17.3 mm?

An inner diameter of 17.3 mm is a US size 7, which is about 54.4 mm in circumference, roughly a UK N½, and a European (ISO) size 54. It sits near the middle of the women's range and toward the low end of the men's range.

What's the difference between diameter and circumference on the chart?

Diameter is the straight-line distance across the inside of the ring; circumference is the distance all the way around the inside. Circumference equals diameter times pi (about 3.14). Charts list both because you measure an existing ring by its diameter but measure a finger by its circumference.

Is the ring size chart the same for men and women?

Yes. Ring sizes aren't gendered, so a US 7 is a US 7 on anyone. Men tend to fall higher on the same chart (commonly 8 to 11) and women lower (commonly 5 to 7), but the millimeter values and conversions are identical.

How accurate is a ring size chart?

The chart itself is exact, since it's a fixed relationship between millimeters and sizes. Accuracy depends on your measurement. Measure at the end of the day when hands are warm, measure more than once, and if you print a chart to measure against, print at 100% scale and verify it against a reference like a credit card (85.6 mm wide).