Electric Motors
Motor Torque Calculator
Calculate shaft torque from shaft power and speed. The default values illustrate the workflow; replace them with measurements or ratings from one documented condition.
Enter values for Shaft torque
Enter ratings or measurements that describe one scenario.
Understanding the equation
For this worksheet, the governing relationship is torque = 9550 × kW ÷ rpm. The formula draws on Shaft power and Speed.
The defaults produce 49.40 N·m. Replace them with measurements from one operating state.
Calculate shaft torque from shaft power and speed. A separate acceleration time result is available from Motor Acceleration Time Calculator.
Applying the result
The primary answer, Shaft torque, describes only the entered scenario. Compare it with starting demand, running current, torque, efficiency, slip, and thermal loading.
Label alternate cases rather than overwriting the baseline. For the companion nearest even pole count calculation, open Motor Poles Frequency Calculator.
Values this page needs
Use nameplate data and measurements from the same load and supply condition. Write down whether each entry is measured, rated, assumed, or calculated.
Values used below a division bar must stay positive. Confirm decimal placement whenever a source uses a different unit scale. If you also need motor efficiency, continue with Motor Efficiency Calculator.
- Shaft power
- Default example: 7.5 kW. Enter shaft power in kW.
- Speed
- Default example: 1450 rpm. Enter speed in rpm.
Practical limits
This is average steady shaft torque.
The equation does not include load inertia, acceleration profile, harmonics, reduced-speed cooling, and mechanical loss. Use measurements, manufacturer data, or another calculation for effects that can change the decision.
Use nameplate data and measurements from the same load and supply condition.
Documenting the calculation
Document shaft power and speed with shaft torque. Keep enough context to reproduce the result later.
Pass shaft torque as the raw numerical value until the final step. Apply standard sizes only after all checks are complete.
A practical checking sequence
Review shaft power and the remaining entries as one case. If one value belongs to another temperature, load, or time period, separate the scenarios.
Use shaft torque alongside nameplate, measured full-load, and actual duty-cycle values. Preserve the unrounded number until all dependent calculations and comparisons are complete.
Document any effect handled outside this page, especially load inertia, acceleration profile, harmonics, reduced-speed cooling, and mechanical loss. That note prevents a later reader from assuming the simple equation covered it.
Questions from practical use
What can cause a different shaft torque reading?
Differences can come from starting method, service factor, enclosure, and thermal duty, measurement uncertainty, or values taken under different conditions.
What is the cleanest way to test another scenario?
Use separate labeled cases when more than one condition changes. Record supply arrangement, speed, duty cycle, enclosure, and winding temperature.
Does Motor Torque Calculator choose a final rating?
Use the number as one check, then review nameplate, measured full-load, and actual duty-cycle values.
What precision should move to the next worksheet?
Keep full precision while transferring shaft torque; round only at the final reporting or selection step.