This calculator allows you to convert from Kilometer/hour to Mach (20°C, 1 atm) and in a reverse direction. To convert from Kilometer/hour to Mach (20°C, 1 atm), enter the amount of Kilometer/hour into the first input and to convert from Mach (20°C, 1 atm) to Kilometer/hour, enter the amount of Mach (20°C, 1 atm) into the second input.