How to calculate your car’s horsepower

You’ve probably heard this word, horsepower, many times before to describe the acceleration power of a car but have you ever wondered how that is figured? I’ve always wondered about that till I saw this mathemathical formula to calculate your car’s horsepower. Here it is:

Power = 2piN * T*1, 34*10-3/ 60

where P = Power, or horsepower
N = Rotational shaft speed or RPM
T = Torque, NM

I need to test this formula myself since I own a Honda Civic Si 2004 and its horspower is 160.