Torque, Speed and Power Calculator
Power from torque and speed, or whichever of the three is missing.
Fill any two fields. The empty one is calculated.
How it works
Mechanical power is torque times angular speed, with speed in radians per second:
P = T × ω, where ω = 2π × n / 60 for a speed n in rpm.
Worked example. A motor gives T = 10 Nm at n = 1500 rpm →
ω = 2π × 1500 / 60 = 157.08 rad/s and
P = 10 × 157.08 = 1570.8 W (1.57 kW).
Rearranged, T = P / ω gives the torque a drive delivers at a given speed, and
ω = P / T the speed at which a torque uses the full power.
Unit converters: Nm to lbf·ft, kW to hp, rpm to rad/s.
Questions
How do I calculate power from torque and rpm?
P = T × ω, with ω = 2π × rpm / 60 in rad/s. 10 Nm at 1500 rpm is 10 × 157.08 = 1570.8 W, or about 1.57 kW.
How much torque does a motor give at a given speed?
T = P / ω. A 1.5 kW motor at 1500 rpm (157.08 rad/s) gives about 9.55 Nm. At constant power, halving the speed doubles the torque.
Why does my hp formula use 5252?
It folds the units into one constant: P[hp] = T[lbf·ft] × rpm / 5252. The calculator converts every unit itself, so torque, speed and power can each be in any unit.