4 ms·

In physics class we used 3,6*m/s to get km/h all the time. It's not superclean but it 3,6 is still pretty easy to multiply or divide with.

• iiv 7y ago
  Well, that is literally how to convert between them. It's not an approximation.
• maury91 7y ago
  It's not an approximation... To convert from m/s to km/h you need to divide by 1000 (there are 1000 meters in 1 km) and multiply by 3600 (there are 3600 seconds in 1 hour). So 3600/1000 = 3.6