Speed / km/h → mph
Convert Kilometers per hour to Miles per hour
Convert linear speeds in metric, customary, and nautical units. Convert Kilometers per hour (km/h) to Miles per hour (mph). Find the formula, worked examples, unit definitions, and practical guidance below.
Reverse: Miles per hour to Kilometers per hour →
How to convert kilometers per hour to miles 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 km/h, b for the intermediate value in m/s, and y for the result in mph.
mph = km/h × 0.2777777777777778 ÷ 0.44704
Worked examples
10 km/h ≈ 6.21371192237 mph
Step 1: (10 × 0.277777777778) ≈ 2.77777777778 m/s.
Step 2: 2.77777777778 ÷ 0.44704 ≈ 6.21371192237 mph.20 km/h ≈ 12.4274238447 mph
Step 1: (20 × 0.277777777778) ≈ 5.55555555556 m/s.
Step 2: 5.55555555556 ÷ 0.44704 ≈ 12.4274238447 mph.
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 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.
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.
Definitions and sources
Carry the same physical assumptions into subsequent physics calculations.
Kilometers per hour to miles per hour reference table
| Kilometers per hour (km/h) | Miles per hour (mph) |
|---|---|
| 1 | 0.621371192237 |
| 5 | 3.10685596119 |
| 10 | 6.21371192237 |
| 25 | 15.5342798059 |
| 50 | 31.0685596119 |
| 100 | 62.1371192237 |
| 1000 | 621.371192237 |
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