Power Calculation (9550 Formula)

How the 9550 Power Formula Works

Rotary power is calculated from torque and rotation speed using the widely used drive formula:

P (kW) = T (Nm) × n (RPM) / 9550

The constant 9550 converts angular velocity into rotations per minute and watts into kilowatts in one step. Enter the torque that the motor delivers in Newton-metres and the rotation speed in RPM; the tool immediately returns the shaft power in kilowatts. It also accounts for a gear reduction ratio: with a reduction of i, the output torque increases while the output speed decreases, exactly as the gearbox multiplies torque.

Efficiency is applied to the adjusted input power so you can check that the chosen motor rating covers the real requirement, helping with electric motor selection and gearbox sizing in machine design.

Why Use This Motor Power Calculator

• Instant results: no unit conversions or manual math — torque, speed and efficiency are handled automatically.
• Motor selection aid: the recommended motor power is rounded up to the nearest standard IEC motor rating in kW and HP.
• Gearbox aware: enter any reduction ratio to see output torque, output speed and required input power.
• Worker-friendly: the calculation details textarea keeps the full formula trace for documentation and verification.

Common Example

A motor running at 1500 RPM with a torque of 100 Nm delivers 100 × 1500 / 9550 = 15.7 kW at the shaft. If the same motor drives a gearbox with a 45:1 reduction, the output speed drops to about 33 RPM while the output torque rises to 4500 Nm — the principle behind most industrial gear drives.