Conversion · United States to Japan

US / Canada to Japan / China ring sizes.

US / Canada 8½ = Japan / China 20 18.52 mm across · 58.2 mm around

Both scales describe the same physical ring. The table below converts every size in the range, derived from inner circumference rather than copied.

US / Canada	Japan / China	Diameter	Circumference
3	5	14.05 mm	44.1 mm
3½	6	14.46 mm	45.4 mm
4	7	14.87 mm	46.7 mm
4½	9	15.27 mm	48.0 mm
5	10	15.68 mm	49.3 mm
5½	12	16.08 mm	50.5 mm
6	13	16.49 mm	51.8 mm
6½	14	16.89 mm	53.1 mm
7	16	17.30 mm	54.3 mm
7½	17	17.71 mm	55.6 mm
8	19	18.11 mm	56.9 mm
8½	20	18.52 mm	58.2 mm
9	21	18.92 mm	59.5 mm
9½	23	19.33 mm	60.7 mm
10	24	19.74 mm	62.0 mm
10½	25	20.14 mm	63.3 mm
11	27	20.55 mm	64.5 mm
11½	outside range	20.95 mm	65.8 mm
12	outside range	21.36 mm	67.1 mm
12½	outside range	21.76 mm	68.4 mm
13	outside range	22.17 mm	69.7 mm
13½	outside range	22.58 mm	70.9 mm

Measure in the evening — fingers swell through the day and in heat — and let your jeweller's own chart take precedence over this one. How to measure at home →