Speed / mph → km/h
Convert Miles per hour to Kilometers per hour
Convert linear speeds in metric, customary, and nautical units. Convert Miles per hour (mph) to Kilometers per hour (km/h). Find the formula, worked examples, unit definitions, and practical guidance below.
Reverse: Kilometers per hour to Miles per hour →
How to convert miles per hour to kilometers per hour
A knot is one international nautical mile (1852 meters) per hour. Mach is excluded because the speed of sound depends on the medium and conditions.
Use x for the value in mph, b for the intermediate value in m/s, and y for the result in km/h.
km/h = mph × 0.44704 ÷ 0.2777777777777778
Worked examples
10 mph ≈ 16.09344 km/h
Step 1: (10 × 0.44704) ≈ 4.4704 m/s.
Step 2: 4.4704 ÷ 0.277777777778 ≈ 16.09344 km/h.20 mph ≈ 32.18688 km/h
Step 1: (20 × 0.44704) ≈ 8.9408 m/s.
Step 2: 8.9408 ÷ 0.277777777778 ≈ 32.18688 km/h.
Results are rounded to 12 significant digits. Converting units does not increase the precision of the original measurement. Very large or small values outside JavaScript’s finite numeric range are rejected.
About Miles per hour
Miles per hour (mph) measures speed under the conventions above. The base value in m/s is (x × 0.44704), where x is the numerical value in mph. Factors shown here are rounded for display; calculations use the stored factor.
About Kilometers per hour
Kilometers per hour (km/h) measures speed under the conventions above. The base value in m/s is (x × 0.277777777778), where x is the numerical value in km/h. Factors shown here are rounded for display; calculations use the stored factor.
Definitions and sources
Carry the same physical assumptions into subsequent physics calculations.
Miles per hour to kilometers per hour reference table
| Miles per hour (mph) | Kilometers per hour (km/h) |
|---|---|
| 1 | 1.609344 |
| 5 | 8.04672 |
| 10 | 16.09344 |
| 25 | 40.2336 |
| 50 | 80.4672 |
| 100 | 160.9344 |
| 1000 | 1609.344 |
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