The standard automotive relationship between an engine’s torque, its rotational speed, and the resulting horsepower it produces.
How it works
Torque in pound-feet is multiplied by RPM and divided by the constant 5,252 to give horsepower.
What this does not include
This does not include deriving torque itself from a force and lever arm — for that starting-point calculation, use this site’s torque calculator instead.
How to use this calculator
- Enter the torque in pound-feet and the engine speed in RPM.
Frequently asked questions
Why does horsepower equal torque at exactly 5,252 RPM?
Because 5,252 is the constant in the formula itself — whenever RPM equals 5,252, the torque and horsepower numbers are mathematically forced to match.
Where does the 5,252 constant come from?
It falls out of the classic mechanical horsepower definition (33,000 ft-lb/min) divided by 2π, which converts rotational speed into the linear terms horsepower is defined by.
Does this work for metric torque units too?
This calculator specifically uses pound-feet — a metric newton-meter torque figure would need converting to pound-feet first for this formula to apply.
