Motor Torque Calculator
Find shaft torque from power and rotational speed.
Results
Shaft torque
Torque at the same shaft power
Electrical input power and shaft output power differ because of motor losses. The constant-power comparison does not describe a motor's full torque–speed curve or starting torque.
Formula · How it works
Formula
T = P × 60 / (2π × n)P = T × 2π × n / 60n = P × 60 / (2π × T)The calculation uses P = Tω and ω = 2πn/60, with power in W, torque in N·m and speed in rpm. The familiar factor 9550 for kW is rounded from 60,000/(2π) ≈ 9549.2966. Imperial hp means mechanical horsepower, approximately 745.6999 W.
Worked example
A shaft delivering 3.7 kW at 1,750 rpm has torque T = 3,700 × 60 / (2π × 1,750) ≈ 20.19 N·m.
How it works
Torque describes the turning effect at the shaft. At constant shaft power, torque decreases as speed increases. This relationship also lets you calculate power from torque and speed, or speed from power and torque.
Common questions
Can I use the electrical input power?
Use shaft output power. If only electrical input is known, first multiply it by the motor efficiency at the operating point.
Why does the result differ slightly from the 9550 formula?
9550 is a rounded conversion factor. This calculator uses the relationship P = T × 2πn/60 directly, so small rounding differences are expected.