mph to km/h Converter (mph to km/h)

How to use this calculator: mph to kmh

1. 1Enter the value measured in mile/hour (mph).
2. 2Confirm the direction is Mile/hour (mph) to Kilometer/hour (km/h); reversing the units changes the factor or offset.
3. 3Apply km/h = mph × 1.60934271. The live converter performs this substitution as you type.
4. 4Read the answer in km/h and keep only justified precision.

Conversion formula

Miles per hour convert to kilometres per hour by multiplying by 1.609344. A 70 mph motorway limit equals about 113 km/h.

The units measure the same quantity at different scales: 1 mph = 1.60934271 km/h, and 1 km/h = 0.62137169 mph.

Worked conversion example: mph to km/h

1. Given: 30 mph
2. Substitute: km/h = 30 × 1.60934271 = 48.28028138
3. Result: 30 mph = 48.28028138 km/h

Accuracy checklist

The converter keeps extra precision internally. Report only the precision supported by the original measurement and follow the required rounding rule.

Direction check: a smaller unit usually gives a larger number; temperature is an exception.

Unit definitions and SI traceability: NIST Office of Weights and Measures — SI Units.