IMPERIAL
Where:
T = Torque in pounds feet
HP = Horsepower
RPM = Engine speed in revolution per minute
Example:
What is the torque of an engine that develops 40 HP at 2500 RPM?
METRIC
Where:
T = Torque in newton metre (N m)
P = Power in watts (W)
RPM = Engine speed in revolutions per minute
Example:
What is the torque of an engine that develops 30,000 W at 2500 rpm?