HP to torque calculator
Enter power and speed for torque, or torque and speed for power. Both directions give the answer in imperial and metric units.
- Torque
- 30.0 lb-ft / 40.7 Nm
Torque in lb-ft equals hp times 5,252 divided by rpm. Halve the speed and you double the torque for the same power.
Where 5,252 comes from
One horsepower is 33,000 foot-pounds per minute. Torque times rotational speed gives power, and the rotation adds a factor of 2 pi per revolution. So hp = T x rpm x 2 pi / 33,000, and 33,000 divided by 2 pi is 5,252. That is the constant, and it is why torque and horsepower curves on a dyno always cross at 5,252 rpm.
In metric the equivalent is kW = T(Nm) x rpm / 9,549. To convert lb-ft to Nm multiply by 1.3558.
Full-load torque of standard motors
A motor nameplate gives horsepower and speed, not torque. This is what those combinations deliver at the shaft, which is what you need to check against a gearbox, coupling or driven machine rating.
| HP | 3,600 rpm | 1,800 rpm | 1,200 rpm | 900 rpm |
|---|---|---|---|---|
| 1 | 1.5 lb-ft / 2.0 Nm | 2.9 / 4.0 | 4.4 / 5.9 | 5.8 / 7.9 |
| 3 | 4.4 / 5.9 | 8.8 / 11.9 | 13.1 / 17.8 | 17.5 / 23.7 |
| 5 | 7.3 / 9.9 | 14.6 / 19.8 | 21.9 / 29.7 | 29.2 / 39.6 |
| 10 | 14.6 / 19.8 | 29.2 / 39.6 | 43.8 / 59.3 | 58.4 / 79.1 |
| 20 | 29.2 / 39.6 | 58.4 / 79.1 | 87.5 / 118.7 | 116.7 / 158.2 |
| 50 | 72.9 / 98.9 | 145.9 / 197.8 | 218.8 / 296.7 | 291.8 / 395.6 |
