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Motor Torque From Power Calculator

Work out motor torque from power instantly with clear inputs, formula shown and shareable results.

About Motor Torque From Power Calculator

Power is torque times angular velocity, so torque equals power divided by 2 pi n / 60. A gearbox trades speed for torque: output torque is input torque times the ratio times gearbox efficiency, while output speed is input speed divided by the ratio.

Formula

Torque from power

T = 9550 x kW / rpm (N·m); after a gearbox T_out = T x ratio x efficiency

Worked example

With the default values below, Motor Torque From Power Calculator returns Torque at the motor shaft of 49.39. Change any input above and every figure here is recalculated in your browser.

Inputs used

Motor power
7.5 kW
Shaft speed
1,450 rpm
Gearbox reduction ratio
5 :1
Gearbox efficiency
95 %

Results

Torque at the motor shaft
49.39 N·m
Torque after the gearbox
234.62 N·m
Output speed
290.00 rpm
Motor torque
36.43 lb·ft

Step by step

  1. 1Values used
  2. 2Torque from power
  3. 3Torque at the motor shaft= 49.39 N·m
  4. 4Torque after the gearbox= 234.62 N·m
  5. 5Output speed= 290.00 rpm
  6. 6Motor torque= 36.43 lb·ft

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

Frequently Asked Questions

Where does 9550 come from?

It is 60,000 / (2 pi), the constant that converts kilowatts and rev/min directly into newton metres.

Does a gearbox create torque from nothing?

No. Power is conserved less losses; the gearbox simply exchanges speed for torque at constant power.

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