Horsepower Calculator
Calculate horsepower from torque and RPM — HP = (torque × RPM) / 5252.
How to Use
- Enter torque (lb-ft) and RPM.
- HP is computed instantly.
- Metric (Nm, kW) shown alongside.
Inputs
Result
Formulas
HP (imperial)
HP = (torque × RPM) / 5252
kW (metric)
kW = (Nm × RPM) / 9549
HP ↔ kW
1 HP = 0.7457 kW
lb-ft ↔ Nm
1 lb-ft = 1.3558 Nm
Frequently Asked Questions
Where does 5252 come from?
The conversion constant for lb-ft and RPM to horsepower: 33 000 ft-lb/min per hp ÷ 2π rad/rev.
Why does HP always equal torque at 5252 RPM?
It's the crossover point of the formula — at 5252 RPM the torque number in lb-ft equals the HP number.
Common Use Cases
Dyno sanity check
Verify shop dyno numbers.
Engine shopping
Compare torque curves to peak HP.
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