If you need to determine automotive torque, revolutions per minute or horsepower and you know 2 of these 3 variables, this will calculate the third.
You can practice using this calculator with these examples:

1) What is the horsepower when an engine is producing 475 foot pounds of torque at 4,000 rpm?

Click on "Horsepower", enter the torque and rpm, click on "Calculate" and the answer is 361.77 horsepower.

2) An engine producing 320 horsepower at 5,000 rpm is producing how much torque?

Click on "Torque", enter the horsepower and rpm, click on "Calculate" and the answer is 336.13 foot pounds.

3) An engine generating 340 horsepower and 400 foot pounds of torque is rotating at what rate?

Click on "RPM", enter horsepower and torque, click "Calculate" and the answer is 4,464.2 rpm.