Table of Comparative Ring-Size Equivalents

United States

Standard

Avg. Diameter

in Inches

British

Equivalent

French

Equivalent

German

Equivalent

Japanese

Equivalent

Swiss

Equivalent
000 0.39 -- -- -- -- --
00 0.422 --- -- -- -- --
0 0.454 -- -- -- -- --
  1/2 -- A -- -- -- --
  3/4 -- A - 1/2 -- -- -- --
1      0.487 B -- -- 1 --
1  1/4 -- B - 1/2 -- -- -- --
1  1/2 0.503 C -- -- -- --
1  3/4 -- C - 1/2 -- -- -- --
2      0.52 D 41  1/2 13  1/4 2 1  1/2
2  1/4 -- D - 1/2 -- --- --- ---
2  1/2 0.536 E 42  3/4 13  3/4 3 2  3/4
2  3/4 -- E - 1/2 -- --- --- ---
3      0.553 F 44      14      4 4     
3  1/8 -- F - 1/2 --- ---   ---
3  3/8 --- G 45  1/4 --- 5 5  1/4
3  1/2 0.569 -- --- 14  1/2 --- ---
3  5/8 -- G - 1/2 --- --- 6 ---
3  3/4 -- H 46  1/2 --- --- 6  1/2
4      0.585 H - 1/2 --- 15      7 ---
4  1/4 -- I 47  3/4 --- --- 7  3/4
4  1/2 0.601 I - 1/2 --- 15  1/4 8 ---
4  7/8 -- J 49      --- --- 9     
5      0.618 J - 1/2 --- 15  3/4 9 ---
5  1/8 -- K 50      --- --- 10     
5  3/8 -- K - 1/2 --- --- 10 ---
5  1/2 0.634 L 51  3/4 16      --- 11  3/4
5  7/8 -- L - 1/2 --- --- 11 ---
6      0.65 M 52  3/4 16  1/2 12 12  3/4
6  1/4 -- M - 1/2 --- --- --- ---
6  1/2 0.666 N 54      17      13 14     
6  3/4 --- N - 1/2 --- --- --- ---
7      0.683 O 55  1/4 17  1/4 14 15  1/4
7  1/4 --- O - 1/2 --- --- --- ---
7  1/2 0.699 P 56  1/2 17  3/4 15 16  1/2
7  3/4 --- P - 1/2 --- --- --- ---
8      0.716 Q 57  3/4 18      16 17  3/4
8  1/4 ---- Q - 1/2 --- --- --- ---
8  1/2 0.732 -- --- 18  1/2 17 ---
8  5/8 --- R 59      --- --- 19     
8  7/8 --- R - 1/2 --- --- --- ---
9      0.748 --- --- 19      18 ---
9  1/8 --- S 60  1/4 --- --- 20  1/4
9  3/8 --- S - 1/2 --- --- --- ---
9  1/2 0.764 --- --- 19  1/2 19 ---
9  5/8 --- T 61  1/2 --- --- 21  1/4
10      0.781 T - 1/2 --- 20      20 ---
10  1/4 --- U 62  3/4 --- 21 22  3/4
10  1/2 0.797 U - 1/2 --- 20  1/4 22 ---
10  5/8 --- V 63  3/4 --- --- 23  3/4
11      0.814 V - 1/2 --- 20  3/4 23 ---
11  1/8 --- W 65      --- --- 25     
11 3/8 --- W - 1/2 --- --- --- ---
11 1/2 0.83 --- --- 21      24 ---
11 5/8 --- X 66  1/4 --- -- 26  1/4
11 7/8 --- X - 1/2 --- --- --- ---
12    0.846 Y 67  1/2 21  1/4 25 27  1/2
12 1/4 --- Y - 1/2 --- --- --- ---
12 1/2 0.862 Z 68  3/4 21  3/4 26 28  3/4
13 3/4 --- Z - 1/2 --- --- --- ---
13    0.879 --- --- 22      27 ---
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