Engineering CalculatorsMotor Torque/Power/Speed Calculator
Solve for any one of torque, power, or speed given the other two (P = T × ω), with common unit conversions built in, plus optional cross-checks for a PM motor's torque constant and efficiency-adjusted electrical input power.
New to P = T·ω? Read the guide: Torque, Power & Speed: The P = T·ω Relationship — a plain-language explainer of the standard behind this calculator.
The core relationship P = T × ω (power = torque × angular velocity) is exact for any rotating shaft, independent of motor type. The optional torque-from-current cross-check (T = Kt × I) is specific to permanent-magnet machines and assumes an ideal, linear torque constant — real motors deviate from this near magnetic saturation or at very high current. The optional efficiency- adjusted electrical input power assumes motoring operation (input greater than output); for regenerative/generating operation the relationship inverts.
Validated: a 1 hp (746 W) motor at a standard 1750 rpm nameplate speed should produce about 4.07 N·m by the classic motor-sizing rule of thumb T[N·m] = 9550 × P[kW] / N[rpm] — this calculator returns 4.071 N·m. The torque-from-current and efficiency cross-checks also match hand calculation exactly (e.g. 10 A at Kt = 0.5 N·m/A → 5.0 N·m; 1000 W mechanical at 92% efficiency → 1086.96 W electrical input).