Electric Motor Torque Calculator
Power & Speed to Torque
T = P × 9550 / n (kW to Nm)
Torque & Speed to Power
P = T × 2π × n / 60
Motor Full Load Current
Estimate full load current for single and three-phase motors
Formula
T = P / ω = P × 9550 / RPM | P = T × ω = T × RPM / 9550 | 1 HP = 746 W | ω = 2π × RPM / 60
Frequently Asked Questions
How do you calculate motor torque from horsepower?
Torque (Nm) = (HP × 746) / (2π × RPM/60), or simplified: Torque (lb-ft) = HP × 5252 / RPM. For example, a 5 HP motor at 1750 RPM produces about 15 lb-ft (20.3 Nm) of torque.
What is the relationship between torque, power, and speed?
Power = Torque × Angular Velocity. In practical units: P(kW) = T(Nm) × n(RPM) / 9550, or P(HP) = T(lb-ft) × n(RPM) / 5252. Doubling the speed at the same torque doubles the power.
How do I estimate motor full load current?
For single-phase: I = P / (V × PF × η). For three-phase: I = P / (√3 × V × PF × η). Where P is input power in watts, V is voltage, PF is power factor, and η is efficiency. Typical motor efficiency is 80-95% and power factor is 0.8-0.9.
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