  ==Hints for conversion factors==  A couple of hints for doing conversion factors :1 pound (avoirdupois) ≡ 0.45359237 kg :1 yard ≡ 0.9144 m those numbers are exact, as many significant digits as you like; that's how the pound and yard and related English units are defined, since the international agreement on a common definition back in 1959. Others include :1 liter ≡ 1 cubic decimeter (from 1901 to 1964, it was 1 L ≈ 1.000028 dm3, a measured relationship) :1 U.S. gallon ≡ 231 in³ (the inch, of course, is 1/36 yd, see above; use the current definition of the inch, 0.9144 m/36 is exactly 0.0254 m) :1 imperial gallon ≡ 4.54609 dm3 (for a while, Canada and the U.K. used slightly different definitions)   