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