0.7874015748 in. Direct Conversion Formula. 20. mm. * 1 in. 25.4. mm. = 0.7874015748 in.
http://wiki.answers.com/Q/What_is_20_mm_in_inches

Your answer is 0.7874 inches. Src:
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20 millimetres is equivalent to 0.79 inches.
http://www.trueknowledge.com/q/what_is_20_mm_in_in...

A square inch is a unit of area that is equal to the sides of a one inch square. The exact measurement for a square inch is 0.00064516m squared.
http://www.ask.com/webanswers/Reference/Other/wha...
