Motor Torque Calculator Formula

Understand the math behind the motor torque calculator. Each variable explained with a worked example.

Use the Motor Torque Calculator

Formulas Used

Full-Load Torque

torque = power_kw * 1000 * 60 / (2 * pi * speed)

Torque in lb-ft

torque_lbft = power_kw * 1000 * 60 / (2 * pi * speed) * 0.7376

Variables

VariableDescriptionDefault
power_kwMotor Rated Power(kW)15
speedMotor Speed(RPM)1455

How It Works

Motor Full-Load Torque

Torque is calculated from the motor nameplate power and rated speed.

Formula

T = P x 60 / (2 pi N) = 9549 P / N

where P is power in watts, N is speed in RPM, and T is torque in N-m. The constant 9549 comes from 60/(2 pi) x 1000 for kW input.

Worked Example

A 15 kW motor running at 1455 RPM.

power_kw = 15speed = 1455
  1. 01T = 15,000 x 60 / (2 x pi x 1455)
  2. 02T = 900,000 / 9,142 = 98.44 N-m
  3. 03T = 98.44 x 0.7376 = 72.61 lb-ft

Ready to run the numbers?

Open Motor Torque Calculator