<P> and for diameter: </P> <P> d = 0.8128 × s + 11.63 (\ displaystyle d = 0.8128 \ times s + 11.63) </P> <Table> Conversion chart for ring sizes <Tr> <Th_colspan="2"> Inside diameter </Th> <Th_colspan="2"> Inside circumference </Th> <Th_colspan="5"> Sizes </Th> </Tr> <Tr> <Th> (in) </Th> <Th> (mm) </Th> <Th> (in) </Th> <Th> (mm) </Th> <Th> United States, Canada and Mexico </Th> <Th> United Kingdom, Ireland, Australia, South Africa and New Zealand </Th> <Th> China, Japan, South America </Th> <Th> India </Th> <Th> Italy, Spain, Switzerland </Th> </Tr> <Tr> <Td> 0.458 </Td> <Td> 11.63 </Td> <Td> 1.44 </Td> <Td> 36.5 </Td> <Td> 0 </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 0.466 </Td> <Td> 11.84 </Td> <Td> 1.46 </Td> <Td> 37.2 </Td> <Td> 1⁄4 </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 0.474 </Td> <Td> 12.04 </Td> <Td> 1.49 </Td> <Td> 37.8 </Td> <Td> 1⁄2 </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 0.482 </Td> <Td> 12.24 </Td> <Td> 1.51 </Td> <Td> 38.5 </Td> <Td> 3⁄4 </Td> <Td> A1⁄2 </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 0.49 </Td> <Td> 12.45 </Td> <Td> 1.54 </Td> <Td> 39.1 </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 0.498 </Td> <Td> 12.65 </Td> <Td> 1.56 </Td> <Td> 39.7 </Td> <Td> 11⁄4 </Td> <Td> B1⁄2 </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 0.506 </Td> <Td> 12.85 </Td> <Td> 1.59 </Td> <Td> 40.4 </Td> <Td> 11⁄2 </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> 0.5 </Td> </Tr> <Tr> <Td> 0.514 </Td> <Td> 13.06 </Td> <Td> 1.61 </Td> <Td> 41 </Td> <Td> 13⁄4 </Td> <Td> C1⁄2 </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 0.522 </Td> <Td> 13.26 </Td> <Td> 1.64 </Td> <Td> 41.7 </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> 1.75 </Td> </Tr> <Tr> <Td> 0.53 </Td> <Td> 13.46 </Td> <Td> 1.67 </Td> <Td> 42.3 </Td> <Td> 21⁄4 </Td> <Td> D1⁄2 </Td> <Td> </Td> <Td> </Td> <Td> 2.25 </Td> </Tr> <Tr> <Td> 0.538 </Td> <Td> 13.67 </Td> <Td> 1.69 </Td> <Td> 42.9 </Td> <Td> 21⁄2 </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 0.546 </Td> <Td> 13.87 </Td> <Td> 1.72 </Td> <Td> 43.6 </Td> <Td> 23⁄4 </Td> <Td> E1⁄2 </Td> <Td> </Td> <Td> </Td> <Td> 3.5 </Td> </Tr> <Tr> <Td> 0.554 </Td> <Td> 14.07 </Td> <Td> 1.74 </Td> <Td> 44.2 </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> 4.25 </Td> </Tr> <Tr> <Td> 0.562 </Td> <Td> 14.27 </Td> <Td> 1.77 </Td> <Td> 44.8 </Td> <Td> 31⁄4 </Td> <Td> F1⁄2 </Td> <Td> 5 </Td> <Td> 5 </Td> <Td> 4.75 </Td> </Tr> <Tr> <Td> 0.57 </Td> <Td> 14.48 </Td> <Td> 1.79 </Td> <Td> 45.5 </Td> <Td> 31⁄2 </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> 5.5 </Td> </Tr> <Tr> <Td> 0.578 </Td> <Td> 14.68 </Td> <Td> 1.82 </Td> <Td> 46.1 </Td> <Td> 33⁄4 </Td> <Td> G1⁄2 </Td> <Td> 6 </Td> <Td> 6 </Td> <Td> 6 </Td> </Tr> <Tr> <Td> 0.586 </Td> <Td> 14.88 </Td> <Td> 1.84 </Td> <Td> 46.8 </Td> <Td> </Td> <Td> </Td> <Td> 7 </Td> <Td> </Td> <Td> 6.75 </Td> </Tr> <Tr> <Td> 0.594 </Td> <Td> 15.09 </Td> <Td> 1.87 </Td> <Td> 47.4 </Td> <Td> 41⁄4 </Td> <Td> H1⁄2 </Td> <Td> </Td> <Td> 7 </Td> <Td> 7.5 </Td> </Tr> <Tr> <Td> 0.602 </Td> <Td> 15.29 </Td> <Td> 1.89 </Td> <Td> 48 </Td> <Td> 41⁄2 </Td> <Td> </Td> <Td> 8 </Td> <Td> 8 </Td> <Td> 8 </Td> </Tr> <Tr> <Td> 0.61 </Td> <Td> 15.49 </Td> <Td> 1.92 </Td> <Td> 48.7 </Td> <Td> 43⁄4 </Td> <Td> </Td> <Td> </Td> <Td> 9 </Td> <Td> 8.75 </Td> </Tr> <Tr> <Td> 0.618 </Td> <Td> 15.7 </Td> <Td> 1.94 </Td> <Td> 49.3 </Td> <Td> 5 </Td> <Td> J1⁄2 </Td> <Td> 9 </Td> <Td> </Td> <Td> 9.25 </Td> </Tr> <Tr> <Td> 0.626 </Td> <Td> 15.9 </Td> <Td> 1.97 </Td> <Td> 50 </Td> <Td> 51⁄4 </Td> <Td> </Td> <Td> </Td> <Td> 10 </Td> <Td> 10 </Td> </Tr> <Tr> <Td> 0.634 </Td> <Td> 16.1 </Td> <Td> 1.99 </Td> <Td> 50.6 </Td> <Td> 51⁄2 </Td> <Td> K1⁄2 </Td> <Td> 10 </Td> <Td> </Td> <Td> 10.5 </Td> </Tr> <Tr> <Td> 0.642 </Td> <Td> 16.31 </Td> <Td> 2.02 </Td> <Td> 51.2 </Td> <Td> 53⁄4 </Td> <Td> </Td> <Td> </Td> <Td> 11 </Td> <Td> 11.25 </Td> </Tr> <Tr> <Td> 0.65 </Td> <Td> 16.51 </Td> <Td> 2.04 </Td> <Td> 51.9 </Td> <Td> 6 </Td> <Td> L1⁄2 </Td> <Td> 11 </Td> <Td> 12 </Td> <Td> 11.75 </Td> </Tr> <Tr> <Td> 0.658 </Td> <Td> 16.71 </Td> <Td> 2.07 </Td> <Td> 52.5 </Td> <Td> 61⁄4 </Td> <Td> </Td> <Td> 12 </Td> <Td> </Td> <Td> 12.5 </Td> </Tr> <Tr> <Td> 0.666 </Td> <Td> 16.92 </Td> <Td> 2.09 </Td> <Td> 53.1 </Td> <Td> 61⁄2 </Td> <Td> M1⁄2 </Td> <Td> 13 </Td> <Td> 13 </Td> <Td> 13.25 </Td> </Tr> <Tr> <Td> 0.674 </Td> <Td> 17.12 </Td> <Td> 2.12 </Td> <Td> 53.8 </Td> <Td> 63⁄4 </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> 13.75 </Td> </Tr> <Tr> <Td> 0.682 </Td> <Td> 17.32 </Td> <Td> 2.14 </Td> <Td> 54.4 </Td> <Td> 7 </Td> <Td> N1⁄2 </Td> <Td> 14 </Td> <Td> 14 </Td> <Td> 14.5 </Td> </Tr> <Tr> <Td> 0.69 </Td> <Td> 17.53 </Td> <Td> 2.17 </Td> <Td> 55.1 </Td> <Td> 71⁄4 </Td> <Td> </Td> <Td> </Td> <Td> 15 </Td> <Td> 15 </Td> </Tr> <Tr> <Td> 0.698 </Td> <Td> 17.73 </Td> <Td> 2.19 </Td> <Td> 55.7 </Td> <Td> 71⁄2 </Td> <Td> O1⁄2 </Td> <Td> 15 </Td> <Td> </Td> <Td> 15.75 </Td> </Tr> <Tr> <Td> 0.706 </Td> <Td> 17.93 </Td> <Td> 2.22 </Td> <Td> 56.3 </Td> <Td> 73⁄4 </Td> <Td> </Td> <Td> </Td> <Td> 16 </Td> <Td> 16.25 </Td> </Tr> <Tr> <Td> 0.714 </Td> <Td> 18.14 </Td> <Td> 2.24 </Td> <Td> 57 </Td> <Td> 8 </Td> <Td> P1⁄2 </Td> <Td> 16 </Td> <Td> 17 </Td> <Td> 17 </Td> </Tr> <Tr> <Td> 0.722 </Td> <Td> 18.34 </Td> <Td> 2.27 </Td> <Td> 57.6 </Td> <Td> 81⁄4 </Td> <Td> Q </Td> <Td> </Td> <Td> </Td> <Td> 17.5 </Td> </Tr> <Tr> <Td> 0.73 </Td> <Td> 18.54 </Td> <Td> 2.29 </Td> <Td> 58.3 </Td> <Td> 81⁄2 </Td> <Td> Q1⁄2 </Td> <Td> 17 </Td> <Td> 18 </Td> <Td> 18.25 </Td> </Tr> <Tr> <Td> 0.738 </Td> <Td> 18.75 </Td> <Td> 2.32 </Td> <Td> 58.9 </Td> <Td> 83⁄4 </Td> <Td> </Td> <Td> </Td> <Td> 19 </Td> <Td> 19 </Td> </Tr> <Tr> <Td> 0.746 </Td> <Td> 18.95 </Td> <Td> 2.34 </Td> <Td> 59.5 </Td> <Td> 9 </Td> <Td> R1⁄2 </Td> <Td> 18 </Td> <Td> </Td> <Td> 19.5 </Td> </Tr> <Tr> <Td> 0.754 </Td> <Td> 19.15 </Td> <Td> 2.37 </Td> <Td> 60.2 </Td> <Td> 91⁄4 </Td> <Td> </Td> <Td> </Td> <Td> 20 </Td> <Td> 20.25 </Td> </Tr> <Tr> <Td> 0.762 </Td> <Td> 19.35 </Td> <Td> 2.39 </Td> <Td> 60.8 </Td> <Td> 91⁄2 </Td> <Td> S1⁄2 </Td> <Td> 19 </Td> <Td> 21 </Td> <Td> 20.75 </Td> </Tr> <Tr> <Td> 0.77 </Td> <Td> 19.56 </Td> <Td> 2.42 </Td> <Td> 61.4 </Td> <Td> 93⁄4 </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> 21.5 </Td> </Tr> <Tr> <Td> 0.778 </Td> <Td> 19.76 </Td> <Td> 2.44 </Td> <Td> 62.1 </Td> <Td> 10 </Td> <Td> T1⁄2 </Td> <Td> 20 </Td> <Td> 22 </Td> <Td> 22 </Td> </Tr> <Tr> <Td> 0.786 </Td> <Td> 19.96 </Td> <Td> 2.47 </Td> <Td> 62.7 </Td> <Td> 101⁄4 </Td> <Td> U </Td> <Td> 21 </Td> <Td> 23 </Td> <Td> 22.75 </Td> </Tr> <Tr> <Td> 0.794 </Td> <Td> 20.17 </Td> <Td> 2.49 </Td> <Td> 63.4 </Td> <Td> 101⁄2 </Td> <Td> U1⁄2 </Td> <Td> 22 </Td> <Td> </Td> <Td> 23.25 </Td> </Tr> <Tr> <Td> 0.802 </Td> <Td> 20.37 </Td> <Td> 2.52 </Td> <Td> 64 </Td> <Td> 103⁄4 </Td> <Td> V </Td> <Td> </Td> <Td> 24 </Td> <Td> 24 </Td> </Tr> <Tr> <Td> 0.81 </Td> <Td> 20.57 </Td> <Td> 2.54 </Td> <Td> 64.6 </Td> <Td> 11 </Td> <Td> V1⁄2 </Td> <Td> 23 </Td> <Td> 25 </Td> <Td> 24.75 </Td> </Tr> <Tr> <Td> 0.818 </Td> <Td> 20.78 </Td> <Td> 2.57 </Td> <Td> 65.3 </Td> <Td> 111⁄4 </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> 25.25 </Td> </Tr> <Tr> <Td> 0.826 </Td> <Td> 20.98 </Td> <Td> 2.59 </Td> <Td> 65.9 </Td> <Td> 111⁄2 </Td> <Td> W1⁄2 </Td> <Td> 24 </Td> <Td> 26 </Td> <Td> 26 </Td> </Tr> <Tr> <Td> 0.834 </Td> <Td> 21.18 </Td> <Td> 2.62 </Td> <Td> 66.6 </Td> <Td> 113⁄4 </Td> <Td> X </Td> <Td> </Td> <Td> </Td> <Td> 26.5 </Td> </Tr> <Tr> <Td> 0.842 </Td> <Td> 21.39 </Td> <Td> 2.65 </Td> <Td> 67.2 </Td> <Td> 12 </Td> <Td> X1⁄2 </Td> <Td> 25 </Td> <Td> 27 </Td> <Td> 27.25 </Td> </Tr> <Tr> <Td> 0.85 </Td> <Td> 21.59 </Td> <Td> 2.67 </Td> <Td> 67.8 </Td> <Td> 121⁄4 </Td> <Td> Y </Td> <Td> </Td> <Td> 28 </Td> <Td> 27.75 </Td> </Tr> <Tr> <Td> 0.858 </Td> <Td> 21.79 </Td> <Td> 2.7 </Td> <Td> 68.5 </Td> <Td> 121⁄2 </Td> <Td> Z </Td> <Td> 26 </Td> <Td> </Td> <Td> 28.5 </Td> </Tr> <Tr> <Td> 0.866 </Td> <Td> 22 </Td> <Td> 2.72 </Td> <Td> 69.1 </Td> <Td> 123⁄4 </Td> <Td> Z1⁄2 </Td> <Td> </Td> <Td> 29 </Td> <Td> 29 </Td> </Tr> <Tr> <Td> 0.874 </Td> <Td> 22.2 </Td> <Td> 2.75 </Td> <Td> 69.7 </Td> <Td> 13 </Td> <Td> </Td> <Td> 27 </Td> <Td> 30 </Td> <Td> 29.75 </Td> </Tr> <Tr> <Td> 0.882 </Td> <Td> 22.4 </Td> <Td> 2.77 </Td> <Td> 70.4 </Td> <Td> 131⁄4 </Td> <Td> Z1 </Td> <Td> </Td> <Td> </Td> <Td> 30.5 </Td> </Tr> <Tr> <Td> 0.89 </Td> <Td> 22.61 </Td> <Td> 2.8 </Td> <Td> 71 </Td> <Td> 131⁄2 </Td> <Td> </Td> <Td> </Td> <Td> 31 </Td> <Td> 31 </Td> </Tr> <Tr> <Td> 0.898 </Td> <Td> 22.81 </Td> <Td> 2.82 </Td> <Td> 71.7 </Td> <Td> 133⁄4 </Td> <Td> Z2 </Td> <Td> </Td> <Td> 32 </Td> <Td> 31.75 </Td> </Tr> <Tr> <Td> 0.906 </Td> <Td> 23.01 </Td> <Td> 2.85 </Td> <Td> 72.3 </Td> <Td> 14 </Td> <Td> Z3 </Td> <Td> </Td> <Td> </Td> <Td> 32.25 </Td> </Tr> <Tr> <Td> 0.914 </Td> <Td> 23.22 </Td> <Td> 2.87 </Td> <Td> 72.9 </Td> <Td> 141⁄4 </Td> <Td> </Td> <Td> </Td> <Td> 33 </Td> <Td> 33 </Td> </Tr> <Tr> <Td> 0.922 </Td> <Td> 23.42 </Td> <Td> 2.9 </Td> <Td> 73.6 </Td> <Td> 141⁄2 </Td> <Td> Z4 </Td> <Td> </Td> <Td> </Td> <Td> 33.5 </Td> </Tr> <Tr> <Td> 0.93 </Td> <Td> 23.62 </Td> <Td> 2.92 </Td> <Td> 74.2 </Td> <Td> 143⁄4 </Td> <Td> </Td> <Td> </Td> <Td> 34 </Td> <Td> 34.25 </Td> </Tr> <Tr> <Td> 0.938 </Td> <Td> 23.83 </Td> <Td> 2.95 </Td> <Td> 74.8 </Td> <Td> 15 </Td> <Td> </Td> <Td> </Td> <Td> 35 </Td> <Td> 34.75 </Td> </Tr> <Tr> <Td> 0.946 </Td> <Td> 24.03 </Td> <Td> 2.97 </Td> <Td> 75.5 </Td> <Td> 151⁄4 </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> 35.5 </Td> </Tr> <Tr> <Td> 0.954 </Td> <Td> 24.23 </Td> <Td> </Td> <Td> 76.1 </Td> <Td> 151⁄2 </Td> <Td> </Td> <Td> </Td> <Td> 36 </Td> <Td> 36.25 </Td> </Tr> <Tr> <Td> 0.962 </Td> <Td> 24.43 </Td> <Td> 3.02 </Td> <Td> 76.8 </Td> <Td> 153⁄4 </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> 36.75 </Td> </Tr> <Tr> <Td> 0.97 </Td> <Td> 24.64 </Td> <Td> 3.05 </Td> <Td> 77.4 </Td> <Td> 16 </Td> <Td> </Td> <Td> </Td> <Td> 37 </Td> <Td> 37.5 </Td> </Tr> </Table> <Tr> <Th_colspan="2"> Inside diameter </Th> <Th_colspan="2"> Inside circumference </Th> <Th_colspan="5"> Sizes </Th> </Tr>

What is a size 9 ring in mm