Horsepower Calculator
Enter any two of horsepower, torque and rpm to solve for the third. The tool uses the standard relationship where horsepower equals torque times rpm divided by 5252.
How to calculate horsepower
- Enter the two values you know: torque, rpm or horsepower.
- Leave the value you want to solve for blank.
- Read the calculated result instantly.
Examples
Torque and rpm to horsepower
300 lb-ft at 5252 rpm
300 hp
Horsepower and rpm to torque
300 hp at 5252 rpm
300 lb-ft
Frequently asked questions
What is the horsepower formula?
Horsepower equals torque in pound-feet times engine speed in rpm, divided by the constant 5252. Rearranged, torque equals hp times 5252 divided by rpm.
Why is the constant 5252?
It comes from the definition of one horsepower as 33,000 lb-ft per minute, divided by 2 times pi. That conversion of rotational power to a per-revolution basis yields 5252.
Why do horsepower and torque curves always cross at 5252 rpm?
Because horsepower equals torque times rpm over 5252, the two values are numerically equal exactly at 5252 rpm, so dyno curves plotted on the same axis cross there.
Do I need to enter all three values?
No. Provide exactly two of horsepower, torque and rpm and the calculator solves for the missing third value.
Is this crank or wheel horsepower?
The formula does not care; it converts whatever torque and rpm you measure. Use crank figures for engine output or wheel figures for power at the tires.
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