International Ring Size Conversion Chart

We are pleased to present the most accurate American to British ring size conversion chart on the web.

United States and Canada UK, Australia, New Zealand, South Africa Diameter Variance (mm)
Circumference (mm) Diameter (mm) Ring Size Circumference (mm) Diameter (mm) Ring Size
36.5 11.6 0
37.2 11.8 ¼ 37.5 11.9 A -0.10
37.8 12.0 ½ 38.1 12.1 -0.10
38.5 12.2 ¾ 38.8 12.3 B -0.09
39.1 12.4 1 39.4 12.5 -0.09
39.7 12.6 40.0 12.7 C -0.09
40.4 12.8 40.6 12.9 -0.08
41.0 13.1 41.3 13.1 D -0.08
41.6 13.3 2 41.9 13.3 -0.07
42.3 13.5 42.5 13.5 E -0.07
42.9 13.7 43.1 13.7 -0.07
43.6 13.9 43.8 13.9 F -0.06
44.2 14.1 3 44.4 14.1 -0.06
44.8 14.3 45.0 14.3 G -0.05
45.5 14.5 45.6 14.5 -0.05
46.1 14.7 46.3 14.7 H -0.04
46.8 14.9 4 46.9 14.9 -0.04
47.4 15.1 47.5 15.1 I -0.04
48.0 15.3 48.1 15.3 -0.03
48.7 15.5 48.8 15.5 J -0.03
49.3 15.7 5 49.4 15.7 -0.02
49.9 15.9 50.0 15.9 K -0.02
50.6 16.1 50.6 16.1 -0.01
51.2 16.3 51.3 16.3 L -0.01
51.9 16.5 6 51.9 16.5 -0.01
52.5 16.7 52.5 16.7 M 0.00
53.1 16.9 53.1 16.9 0.00
53.8 17.1 53.8 17.1 N 0.01
54.4 17.3 7 54.4 17.3 0.01
55.0 17.5 55.0 17.5 O 0.02
55.7 17.7 55.6 17.7 0.02
56.3 17.9 56.3 17.9 P 0.02
57.0 18.1 8 56.9 18.1 0.03
57.6 18.3 57.5 18.3 Q 0.03
58.2 18.5 58.1 18.5 0.04
58.9 18.7 58.8 18.7 R 0.04
59.5 18.9 9 59.4 18.9 0.05
60.2 19.1 60.0 19.1 S 0.05
60.8 19.4 60.6 19.3 0.05
61.4 19.6 61.3 19.5 T 0.06
62.1 19.8 10 61.9 19.7 0.06
62.7 20.0 10¼ 62.5 19.9 U 0.07
63.3 20.2 10½ 63.1 20.1 0.07
64.0 20.4 10¾ 63.8 20.3 V 0.08
64.6 20.6 11 64.4 20.5 0.08
65.3 20.8 11¼ 65.0 20.7 W 0.08
65.9 21.0 11½ 65.6 20.9 0.09
66.5 21.2 11¾ 66.3 21.1 X 0.09
67.2 21.4 12 66.9 21.3 0.10
67.8 21.6 12¼ 67.5 21.5 Y 0.10
68.5 21.8 12½ 68.1 21.7 0.11
69.1 22.0 12¾ 68.8 21.9 Z 0.11
69.7 22.2 13 69.4 22.1 0.11
70.4 22.4 13¼ 70.0 22.3 Z1 0.12
71.0 22.6 13½ 70.6 22.5 Z1½ 0.12
71.6 22.8 13¾ 71.3 22.7 Z2 0.13
72.3 23.0 14 71.9 22.9 Z2½ 0.13
72.9 23.2 14¼ 72.5 23.1 Z3 0.13
73.6 23.4 14½ 73.1 23.3 Z3½ 0.14
74.2 23.6 14¾ 73.8 23.5 Z4 0.14
74.8 23.8 15 74.4 23.7 Z4½ 0.15
75.5 24.0 15¼ 75.0 23.9 Z5 0.15
76.1 24.2 15½ 75.6 24.1 Z5½ 0.16
76.8 24.4 15¾ 76.3 24.3 Z6 0.16
77.4 24.6 16 76.9 24.5 Z6½ 0.16

** The diameter variance is the difference between the American Sizes and the British sizes. For example, a US size 4 has a diameter of 14.9mm (rounded up) and a UK H 1/2 has a diameter of 14.9 (rounded down). Because of rounding, the US size 4 is 0.04 mm smaller than the UK H 1/2.