Motor Torque Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/6/2026
A motor's torque is calculated with C = (P × 60,000) ÷ (2π × N), where P is the power in kW and N the rotational speed in rpm. For a 10 kW motor running at 3000 rpm, the torque is about 31.8 N·m.
Explanation
Torque measures the rotational force a motor can exert on its shaft, expressed in newton-meters (N·m). It is derived from power and angular velocity through the relationship P = C × ω, where ω (in radians per second, see our angular velocity calculator) equals 2π × N ÷ 60 for a speed N expressed in revolutions per minute. Rearranging this relationship and expressing power in kilowatts gives C = (P × 60,000) ÷ (2π × N). For the same power, a motor that turns more slowly therefore delivers more torque, and vice versa: this is why low-speed electric motors (such as certain traction motors) are designed for high torque, while a motorcycle's combustion engine runs at high revs with lower unit torque, compensated by a gearbox. This formula gives the average torque delivered in steady-state operation; it doesn't represent the instantaneous torque in a combustion engine, which varies throughout the cycle. For the electrical power drawn by a three-phase motor, see our electrical power calculator.
Example: a 10 kW motor at 3000 rpm
Inputs
Power: 10 kW. Rotational speed: 3000 rpm.
Calculation
Torque = (10 × 60,000) ÷ (2 × π × 3000) = 600,000 ÷ 18,849.6… ≈ 31.83 N·m.
Result
This motor delivers a torque of about 31.8 N·m at this speed.
Frequently asked questions
Why does torque decrease as rotational speed increases, for the same power?
Because power is the product of torque and angular velocity (P = C × ω): at constant power, torque and rotational speed are inversely proportional. It's the same logic as a multi-speed bicycle: for the same effort (power), a small gear spins the pedals faster with less force per turn, while a large gear needs more force but fewer turns.
Does this calculator give the exact torque of a combustion engine at every instant?
No. For a combustion engine, the actual torque fluctuates throughout each combustion cycle and depends heavily on engine speed (a torque curve specific to each engine, non-linear). This formula calculates a theoretical average torque from rated power and speed, a useful approximation for an electric motor in steady-state operation, but only indicative for a combustion engine.
What happens if the rotational speed is zero?
The calculation is undefined: a stopped motor cannot be characterized by this relationship between power and rotational speed (its instantaneous power is also zero). The calculator then shows a value as unavailable rather than a misleading result like zero.