metric = metric
1 millimeter = .03937 inch
1 centimeter = 10 millimeters
1 decimeter = 10 centimeters
1 meter = 10 decimeters
1 decameter = 10 meters
1 hectometer = 10 decameter
1 kilometer = 10 hectometers
1 myriameter = 10 kilometers

metric = U.S.
1 kilometer = 0.621 mile = 3,280.8 feet
1 meter = 3.2808 feet = 39.37 inches
1 centimeter = 0.3937 inch

U.S. = metric
1 mile = 1.609 kilometers = 1609.3 meters
1 yard = 0.914 meter = 9.144 decimeters
1 foot = 0.3048 meter = 30.480 centimeters
1 inch = 2.540 centimeters = 25.40 millimeters

practical equivalents
A 6' man is also 183 centimeters tall.
A 5'3" woman is 160 centimeters tall.
A 12' traffic lane is 365.76 centimeters or 3.6576 meters  wide.
A speed of 45 miles-per-hour is also 72 kilometers-per-hour.
A 24" T.V. screen is 61 centimeters.
A standard doorway is 81 centimeters x 203 centimeters.
A mile is 1,999 feet longer than a kilometer.
A meter is 3.37 inches longer than a yard.
A 8 1/2" x 11" sheet of paper is 22 x 28 centimeters.
A new pencil is 19 centimeters long.
A 500 foot home run is 167 yards or 152 meters.
A 35-yard pass is 105 feet or 32 meters.

abbreviations
millimeter - mm
centimeter - cm
decimeter - dm
meter - m
dekameter - dkm
hectometer - hm
kilometer - km
myriameter - mym