When to use this calculator
Find shaft torque from mechanical power and rotational speed. Use mechanical shaft output power, not electrical input power unless efficiency is applied.
Explore the ac power & reactance calculators for other questions in this topic. For a related calculation, use the Motor Synchronous Speed Calculator: Find synchronous rotating-field speed from frequency and pole count.
PUTTING IT INTO PRACTICE
Motor Shaft Torque: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Mechanical shaft power (kW) | 15 |
| Shaft speed (rpm) | 1,500 |
| Result | 95.492966 N·m |
- Check the input labels and enter the example values above.
- Apply the relationship: Torque = power in watts/(rpm×2π/60).
- The result is 95.492966 N·m, rounded for display.
How to interpret your result
Use mechanical shaft output power, not electrical input power unless efficiency is applied.
Use RMS values in the AC power relationships. Apparent power is measured in VA and real power in watts. Pure-sine conversions and balanced three-phase equations only apply under their stated assumptions.
Frequently asked questions
Why can volt-amps differ from watts?
Apparent power is the RMS voltage-current product, while real power also reflects power factor. They are numerically equal only at a power factor of one.
When is the motor shaft torque calculator useful?
Find shaft torque from mechanical power and rotational speed. Use mechanical shaft output power, not electrical input power unless efficiency is applied.
How do I use the motor shaft torque calculator?
Enter mechanical shaft power (kw), shaft speed (rpm). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Torque = power in watts/(rpm×2π/60).
What should I check before using the result?
Use mechanical shaft output power, not electrical input power unless efficiency is applied.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
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