km/h to mph Converter - Kilometer per Hour to Mile per Hour

Conversion derivation

Express both km/h and mph in the same base unit m/s (meter per second), then cancel the shared base unit.

1. 1

   Rewrite km/h in the base unit

   $$1km/h=0.277778m/s$$
2. 2

   Rewrite mph in the base unit

   $$1\mathrm{mph}=0.44704m/s$$
3. 3

   Forward conversion

   $$\begin{array}{rl}1km/h& =\frac{0.277778\cancel{m/s}}{0.44704\cancel{m/s}}\times 1\mathrm{mph}\\ & =\frac{0.277778}{0.44704}\mathrm{mph}\\ & =0.621371689334\mathrm{mph}\end{array}$$
4. 4

   Reverse conversion

   $$\begin{array}{rl}1\mathrm{mph}& =\frac{0.44704\cancel{m/s}}{0.277778\cancel{m/s}}\times 1km/h\\ & =\frac{0.44704}{0.277778}km/h\\ & =1.60934271253km/h\end{array}$$