Motor Torque Calculator

Calculate motor output torque based on power and rotational speed.

Torque (Newton-meters): 0.00 Nm
Torque (Foot-pounds): 0.00 lb-ft
Torque (Inch-pounds): 0.00 in-lb

What is Motor Torque?

Torque is a measure of the rotational force produced by a motor's shaft. Unlike power, which measures the rate at which work is performed, torque measures the capacity of the motor to turn a load. In mechanical engineering and automotive applications, understanding the relationship between power, speed, and torque is essential for selecting the correct motor for a specific application.

How to Calculate Motor Torque

The relationship between Power (P), Torque (T), and Rotational Speed (n) is defined by a standard physics formula. Depending on the units used, the constants in the formula change:

  • In Metric Units (Nm): T = (P[kW] × 9548.8) / RPM
  • In Imperial Units (lb-ft): T = (HP × 5252) / RPM

When you use our Motor Torque Calculator, the tool automatically handles these unit conversions for you. You simply need to provide the power rating and the shaft speed in Revolutions Per Minute (RPM).

Why Torque Matters in Engineering

Torque is critical because it determines if a motor can actually start a load from a standstill. High-torque motors are required for heavy machinery, lifting equipment, and electric vehicles that need to accelerate quickly. Conversely, high-speed motors with lower torque are often used in fans and blowers where the initial resistance is low.

Frequently Asked Questions

What is the difference between Torque and Horsepower?

Horsepower is the total amount of work done over time, while torque is the actual turning force. Think of torque as the "muscle" and horsepower as the "speed" at which that muscle works.

Can I find RPM if I have Torque and Power?

Yes, by rearranging the formula: RPM = (Power × Constant) / Torque. Our calculator is designed to solve for torque as the primary unknown, but the mathematical relationship remains consistent.

How does an AC motor's speed affect torque?

For most standard electric motors, as the speed (RPM) increases while power remains constant, the available torque decreases. This is why many industrial machines use gearboxes to reduce speed and increase usable torque for heavy tasks.