The following article on metric system conversion was originally printed in Tactical and Technical Trends, No. 29, July 15, 1943. [DISCLAIMER: The following text is taken from the U.S. War Department publication Tactical and Technical Trends. As with all wartime intelligence information, data may be incomplete or inaccurate. No attempt has been made to update or correct the text. Any views or opinions expressed do not necessarily represent those of the website.]

INCH EQUIVALENTS OF MILLIMETER MEASUREMENTS In reading European specifications expressed in metric terms, Americans often have difficulty in translating them into English equivalents. The following table may be helpful:  MM      Inch            MM     Inch    1 .039  19  .758   2 .079  20  .787   3 .118  25  .984   4 .157  30 1.181   5 .197  35 1.378   6 .236  40 1.575   7 .276  45 1.772   8 .315  50 1.939   9 .354  55 2.165  10 .394  60 2.362  11 .433  65 2.559  12 .472  70 2.756  13 .512  75 2.953  14 .551  80 3.150  15 .591  85 3.346  16 .630  90 3.543  17 .669  95 3.740  18 .709 100 3.937     105 4.134 Approximate armor thickness usually met with on German Tanks: MM     Inch           MM     Inch  5  .20  22  .87 10  .39  26 1.02 12  .47  30 1.18 14  .55  50 1.97 15  .59  62 2.44 18  .71  82 3.23 20  .79 102 4.02 Land gun calibers--(G) for German, (J) for Japanese, (I) for Italian, (F) for French (captured), and (R) for Russian (captured). Designations of countries not necessarily exclusive. MM         Inch           MM         Inch 6.5 (I-J)  .256 76.2 (R)  3.000 7.5 (F)  .295 81 (G-J-F)  3.189 7.62 (R)  .300 88 (G)  3.465 7.7 (J-I)  .303 100 (G)  3.937 7.92 (G)  .312 105 (G-J)  4.134 8.0 (J-I-F)  .315 122 (R)  4.799 9.0 (G-I)  .354 150 (G)  5.906 12.7 (I-J)  .500 152 (R)  5.985 13 (J)  .512 155 (F-J)  6.102 15 (G)  .591 170 (G)  6.693 20 (G-I-J)  .787 200 (J)  7.874 25 (F)  .984 203 (R)  7.992 28 (G) 1.102 210 (G)  8.268 30 (G) 1.181 240 (G-J)  9.449 37 (G-J-I) 1.457 280 (G-R) 11.024 46 (G) 1.811 300 (G) 11.811 47 (I) 1.850 305 (G) 12.007 50 (G-J-R) 1.969 350 (G) 13.779 70 (J) 2.756 380 (G) 14.961 75 (F-G-I) 2.953 610 (G) 24.016 NOTE: According to the metric system, the meter is split up into tenths, hundredths, thousandths. Latin prefixes are used: deci    =   1/10 centi   =   1/100 milli   =   1/1000 For larger measures, Greek prefixes are used: Deka   =   10 Hecto   =   100 Kilo   =   1000 Thus we have the following measurement basis: 10 millimeters (mm)   =   1 centimeter (cm) 10 cm   =   1 decimeter (dm) 10 dm   =   1 meter (m) 10 m   =   1 Dekameter (Dm) 10 Dm   =   1 Hectometer (Hm) 10 Hm   =   1 Kilometer (Km) 1 inch   =   2.5 cm (approx) 5 miles   =   8 Km 1 Km   =   .621 mile (approx 5/8)

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