Electrical · Free Calculator
Motor Torque Calculator
Convert between shaft power, speed and torque for motors, gearboxes and pumps.
kW to N·mHP to lbf·ftTorque to powerAny speed
rpm
Torque97.44 N·m
Torque71.87 lbf·ft
Torque9.936 kgf·m
How this result was calculated
- T = 9549.3 × P(kW) ÷ n = 9549.3 × 15 ÷ 1,470 = 97.44 N·m
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Torque and Power Formula
T (N·m) = 9549.3 × P (kW) ÷ n (rpm)
P (kW) = T × n ÷ 9549.3
P (kW) = T × n ÷ 9549.3
The constant 9549.3 is 60,000 ÷ 2π, which converts rpm to radians per second and watts to kilowatts.
Worked example
A 15 kW motor at 1470 rpm delivers T = 9549.3 × 15 ÷ 1470 = 97.4 N·m.
Key insight: a gearbox multiplies torque by its ratio (less efficiency losses) while dividing speed, so power stays nearly constant.
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Frequently Asked Questions
How do I calculate motor torque from kW?
Multiply kW by 9549.3 and divide by the speed in rpm to get N·m.
What is the torque of a 1 HP motor at 1440 rpm?
1 HP = 0.7457 kW, so T = 9549.3 × 0.7457 ÷ 1440 = 4.95 N·m.
Why does starting torque differ from rated torque?
Induction motors produce 150 to 250 % of rated torque at start, depending on design. Check the motor curve for starting requirements.
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