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Gurukrupa Enterprises
Mechanical Calculators

RPM Calculator

Calculate rotational speed (RPM) from power and torque.

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About this calculator

This calculator rearranges the standard power–torque–speed relationship to find rotational speed (RPM) when power and torque are known — useful for checking a drive's expected running speed against a gearbox or pulley ratio.

Formula

N (RPM) = (P × 9550) ÷ T
  • PShaft power — kilowatts
  • TTorque — newton-metres
  • NRotational speed — RPM

Worked Example

Given: A drive delivers 15 kW at 99.5 N·m of torque.

Result: N = (15 × 9550) ÷ 99.5 = 1440 RPM.

How to Use

  1. Enter the shaft power in kW.
  2. Enter the torque in N·m.
  3. Click Calculate to get the rotational speed in RPM.

Important Assumptions

  • Steady-state operation only.

Common Mistakes

  • Mixing torque units — if torque is in kgf·m rather than N·m, convert first (1 kgf·m ≈ 9.81 N·m).

Frequently Asked Questions

Can I use this for gearbox output speed?

Yes, if you use the torque and power values measured or rated at the gearbox output shaft rather than the motor input shaft.

These calculators are provided for informational and estimation purposes. Results depend on the assumptions and input values used. Always verify critical engineering calculations against applicable standards, manufacturer specifications, site measurements, and qualified professional advice.