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Motor Torque Calculator

Enter shaft output power and speed at the operating point to find its average torque. Power and speed must refer to the same shaft.

Local calculation · inputs stay in your browser

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    An input link contains the values you entered. Share only information you want to disclose.

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    Formula and method

    ω = 2πn / 60; T = 1000P / ω = (30000/π)P/n ≈ 9549.297P/n. P is in kW, n in rpm and T in N·m; lbf·ft = N·m / 1.3558179483314004.

    Worked example

    7.5 kW shaft output at 1450 rpm gives approximately 49.393 N·m (36.430 lbf·ft).

    Assumptions and limits

    • Use shaft output power, not electrical input. If only electrical input is known, multiply it by efficiency first; do not apply efficiency again to shaft power.
    • The common engineering coefficient 9550 is rounded from 9549.297. This tool uses the coefficient derived from π.
    • This relationship does not establish starting, stall or peak torque. Torque cannot be found by dividing power by zero speed. For a gearbox output, use output power and output speed.

    Frequently asked questions

    Can I use synchronous speed instead of nameplate speed?

    For rated torque of an induction motor, use its actual speed at rated load. Synchronous speed omits slip and changes the result.

    Does halving speed double torque at equal power?

    The equation P = Tω gives that result, provided the motor or drive can continuously deliver the same shaft power at the lower speed. Check its torque curve and thermal limits.

    References

    Motor Torque Calculator practical guide and common questions

    What does Motor Torque Calculator calculate?

    Enter shaft output power and speed at the operating point to find its average torque. Power and speed must refer to the same shaft. ω = 2πn / 60; T = 1000P / ω = (30000/π)P/n ≈ 9549.297P/n. P is in kW, n in rpm and T in N·m; lbf·ft = N·m / 1.3558179483314004.

    When is this useful?

    7.5 kW shaft output at 1450 rpm gives approximately 49.393 N·m (36.430 lbf·ft).

    How do I enter the inputs?

    Enter the inputs for Motor Torque Calculator: Mechanical shaft output power, Actual speed of the same shaft. Calculate, check the units and assumptions, then copy or download the results.

    How should I interpret the results?

    Use shaft output power, not electrical input. If only electrical input is known, multiply it by efficiency first; do not apply efficiency again to shaft power. The common engineering coefficient 9550 is rounded from 9549.297. This tool uses the coefficient derived from π. This relationship does not establish starting, stall or peak torque. Torque cannot be found by dividing power by zero speed. For a gearbox output, use output power and output speed.

    Where are my inputs processed?

    Motor Torque Calculator runs in this browser. Inputs are not uploaded to a calculation server; copying and CSV download require your action. The existing site analytics and advertising still load.