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Gurukrupa Enterprises
Mechanical Calculators

Torque Calculator

Calculate shaft torque from power and rotational speed (RPM).

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About this calculator

This calculator finds the torque transmitted by a rotating shaft from its power and speed, using the standard relationship between power, torque and angular velocity (P = T × ω). The constant 9550 converts kW and RPM directly into torque in newton-metres.

Formula

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

Worked Example

Given: A 15 kW motor runs at 1440 RPM.

Result: T = (15 × 9550) ÷ 1440 = 99.5 N·m.

How to Use

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

Important Assumptions

  • Assumes steady-state rotation at the given power and speed (not starting or transient torque).

Common Mistakes

  • Using motor output HP directly without converting to kW first.
  • Confusing motor nameplate 'full load torque' (already given by the manufacturer) with this calculated value — use the manufacturer's figure for critical designs.

Frequently Asked Questions

Where does the constant 9550 come from?

It is derived from P(W) = T(N·m) × ω(rad/s), with ω = 2πN/60, rearranged and simplified for P in kW and N in RPM: 9550 ≈ 60,000/(2π).

Does this give starting torque or running torque?

This gives the steady running torque at the stated power and speed. Motor starting torque is a separate nameplate/design value.

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.