Zerdly

Shaft Power, Torque & Speed Calculator

Converts between shaft power, torque and rotational speed for a rotating drive.

100% FreeRuns in your browserProfessional
How to use this calculator

Enter Values

Minimum 0

Minimum 0

Minimum 0

Enter your values and press Calculate to see results.

Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.

How to use this calculator

  1. Enter any two of power (kW), rotational speed (rpm) and torque (N·m).
  2. The calculator works out the third.
  3. Read all three values together.

How it works

For steady rotation, power, torque and speed are linked by T (N·m) = 9549 · P (kW) / N (rpm), where 9549 = 60,000 / 2π.

Give it any two and it solves the remaining one — handy for sizing motors, gearboxes and drives.

Worked example

15 kW at 1450 rpm. T = 9549 × 15 / 1450 ≈ 98.8 N·m — the torque that motor delivers at full load.

Tips

  • For horsepower, 1 hp ≈ 0.7457 kW — convert first, then use this tool.

Frequently asked questions

Is this input or output power?

The formula relates power, torque and speed at the same shaft. Across a gearbox or belt drive, multiply by the efficiency to get the output power, then recompute torque at the output speed.

Can I use these results for final design?

No. These calculators are for first-pass sizing, checking and learning. They assume ideal supports, static loads and elastic behaviour, and they don't apply load factors, member capacity, buckling or connection checks. Always verify against the relevant design code (e.g. AS 4100, AS 1170, Eurocode) and have a qualified engineer sign off structural work.

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Cite this tool

Zerdly. (2026). Shaft Power, Torque & Speed Calculator. Retrieved from https://www.zerdly.com/tools/shaft-power-torque-speed-calculator/

Tip: Enter any known values to calculate the remaining results.

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