Ring Size Converter USA sizeDiam. inch.Diam. mmCircum. mm00000001/23/411 1/41 1/21 3/422 1/42 1/22 3/433 1/83 1/43 3/83 1/23 5/83 3/444 1/44 1/24 5/84 3/455 1/85 1/45 3/85 1/25 3/45 7/866 1/46 1/26 3/477 1/47 1/27 3/488 1/48 1/28 5/88 3/48 7/899 1/89 1/49 3/89 1/29 5/89 3/41010 1/410 1/210 5/810 3/41111 1/811 1/411 3/811 1/211 5/811 3/411 7/81212 1/212 3/413 .390.422.454.474.482.487 —.503 —.520 —.536 —.553 — — —.569 — —.585 —.601 — —.618 — — —.634 — —.650 —.666 —.683 —.699 —.716 —.732 — — —.748 — — —.764 — —.781 —.797 — —.814 — — — —.830 — —.846.862 —.879 9.9110.7211.5311.9512.1812.3712.6012.7813.0013.2113.4113.6113.8314.0514.1514.2514.3614.4514.5614.6514.8615.0415.2715.4015.5315.7015.8015.9016.016.1016.3016.4116.5116.7116.9217.1317.3517.4517.7517.9718.1918.3518.5318.6118.6918.8018.8919.1019.2219.3119.4119.5119.6219.8420.0220.2020.3220.4420.6820.7620.8520.9421.0821.1821.2421.3021.4921.8922.1022.33 31.133.736.237.538.338.939.640.240.841.542.142.743.444.044.344.644.945.245.645.946.547.147.848.148.449.049.349.650.050.350.951.351.552.252.853.454.054.755.355.956.657.257.858.458.459.059.159.459.760.060.360.660.961.662.262.863.163.564.164.364.765.065.365.766.066.366.667.968.569.1 BritishFrenchGermanJapaneseSwiss — — —AA 1/2BB 1/2CC 1/2DD 1/2EE 1/2FF 1/2 —G —G 1/2HH 1/2I I 1/2J —J 1/2K —K 1/2L —L 1/2MM 1/2NN 1/2OO 1/2PP 1/2QQ 1/2 —R —R 1/2 —S —S 1/2 —T —T 1/2UU 1/2V —V 1/2W —W 1/2 —X —X 1/2YZZ 1/2 — — — — — — — — — —41 1/2 —42 3/4 —44 — —45 1/4 — —46 1/2 —47 3/4 —49 — —50 — —51 3/4 — —52 3/4 —54 —55 1/4 —56 1/2 —57 3/4 — —59 — — —60 1/4 — — —61 1/2 — —62 3/4 —63 — —65 — — —66 1/4 — —67 1/268 3/4 — — — — — — — — — — —13 1/2 —13 3/4 —14 — — —14 1/2 — —15 —15 1/415 1/2 —15 3/4 — — —16 — —16 1/2 —17 —17 1/4 —17 3/4 —18 —18 1/2 — — —19 — — —19 1/2 — —20 —20 1/4 — —20 3/4 — — —21 — — —21 1/421 3/4 —22 — — — — —1 — — —2 —3 —4 — —5 —6 —7 —8 — —9 — —10 — — —12 —13 —14 —15 —16 —17 — — —18 — — —19 — —202122 — —23 — — —24 — — —2526 —27 — — — — — — — — —1 1/2 —2 3/4 —4 — —5 1/4 — —6 1/2 —7 3/4 —9 — —10 — —11 3/4 — —12 3/4 —14 —15 1/4 —16 1/2 —17 3/4 — —19 — — —20 1/4 — — —21 1/2 — —22 3/4 —23 3/4 — —25 — — —26 1/4 — —27 1/228 3/4 — —