1 centimetre (cm) = 10 millimetres (mm)
==> Set mmPerCm = 10

1 metre (m) = 100 cm = 1,000 mm
= mmPerCm * cmPerMetre mm
==> Set cmPerMetre = 100
==> Set mmPerMetre = 1000

1 kilometre (km) = 1,000 m
==> Set metresPerKm = 1000

1 foot (ft) = 12 inches (in)
==> Set inchesPerFoot = 12

1 yard (yd) = 3 ft
= 3 * inchesPerFoot in
= 36 in
==> Set feetPerYard = 3

1 mile (mi) = 5,280 ft
= 5,280 / feetPerYard yd
= 1,760 yd
==> Set feetPerMile = 5,280

1 cm
= mmPerCm / mmPerInch in
= 1 / 2.54 in
= mmPerCm / ( mmPerInch * inchesPerFoot) ft
= 1 / 30.48 ft
= mmPerCm / ( mmPerInch * inchesPerFoot * feetPerYard ) yd
= 1 / 91.44 yd

1 m
= mmPerMetre / mmPerInch in
= 1,000 / 25.4 in
= mmPerMetre / ( mmPerInch * inchesPerFoot ) ft
= 1,000 / 304.8 ft
= mmPerMetre / ( mmPerInch * inchesPerFoot * feetPerYard ) yd
= 1,000 / 914.4 yd

1 km
= mmPerMetre * metresPerKm / ( mmPerInch * inchesPerFoot ) ft
= 1,000 / 0.3048 ft
= mmPerMetre * metresPerKm / ( mmPerInch * inchesPerFoot * feetPerYard ) yd
= 1,000 / 0.9144 yd
= mmPerMetre * metresPerKm / ( mmPerInch * inchesPerFoot * feetPerMile ) mi
= 1 / 1.609344 mi