This calculator allows you to convert from Millijoule/second to Horsepower (550 ft*lbf/s) and in a reverse direction. To convert from Millijoule/second to Horsepower (550 ft*lbf/s), enter the amount of Millijoule/second into the first input and to convert from Horsepower (550 ft*lbf/s) to Millijoule/second, enter the amount of Horsepower (550 ft*lbf/s) into the second input.