CONVERSION FROM ONE SYSTEM OF UNITS TO ANOTHER

There are many instances when an engineer wishes to convert into SI units a numerical result obtained in U.S. customary units or vice versa. Because the unit of time is the same in both systems, only two kinetic base units need be converted. Thus, since all other kinetic units can be derived from these base units, only two conversion factors need be remembered. 

Units of Length.   By definition the U.S. customary unit of length is 

1 ft = 0.3048 m 

it follows that :

1  m i55280 ft55280(0.3048 m)51609 m 

or

1 mi51.609 km

also

            

or

1 in. 525.4  mm