Electric Motor Torque Calculator

What Is Electric Motor Torque?

Torque is a twisting force. In motors, it describes how strongly the motor shaft can rotate an object.

• Torque tells you how much load the motor can move
• Speed tells you how fast it can move that load
• Power connects torque and speed together

Torque is usually measured in:

• Newton-meters (Nm)
• Pound-feet (lb-ft)
• Kilogram-meters (kg-m)

A simple way to think about torque is this:
A motor with high torque can turn heavy things. A motor with low torque can only turn light things.

Why Torque Matters More Than You Think

Many people choose motors based on power alone. That often leads to problems.

Torque affects:

• Starting ability
• Load handling
• Acceleration
• Mechanical stress
• Motor lifespan

For example:

• A conveyor belt needs high torque at low speed
• A fan needs low torque at high speed
• A robot arm needs stable torque across motion

This is why a torque calculator is so useful. It shows whether a motor matches the job before you install it.

What the Electric Motor Torque Calculator Does

This calculator estimates motor torque using three different methods. Each method fits a different real-world situation.

You choose the calculation type, enter the values, and the calculator converts units, applies formulas, and shows the results in multiple torque units.

The calculator supports:

• Power and speed
• Force and radius
• Current and motor constant
• Efficiency adjustment
• Multiple unit systems
• Torque interpretation in plain language

Method 1: Torque from Power and Speed

When to Use This Method

Use this when you know:

• Motor power (kW, HP, or W)
• Motor speed (RPM or rad/s)
• Motor efficiency

This is the most common method for industrial motors.

Formula Used

Torque (Nm) = Power (W) ÷ Angular Speed (rad/s)

The calculator:

1. Converts power to watts
2. Applies efficiency
3. Converts speed to radians per second
4. Calculates torque
5. Converts torque into lb-ft and kg-m

Example

• Power: 5 kW
• Speed: 1500 RPM
• Efficiency: 85%

The calculator estimates how much usable torque the motor delivers at that speed.

It also shows calculated power from torque, which helps verify results.

Method 2: Torque from Force and Radius

When to Use This Method

Use this when torque comes from a physical force applied at a distance, such as:

• Pulleys
• Gears
• Levers
• Wheels

Formula Used

Torque (Nm) = Force (N) × Radius (m)

The calculator:

• Converts force units (N, lbf, kgf)
• Converts distance units (m, cm, mm, ft, in)
• Calculates torque in Nm
• Converts results to lb-ft and kg-m

Example

• Force: 100 N
• Radius: 0.5 m

Torque = 50 Nm

This method is simple and very accurate for mechanical systems.

Method 3: Torque from Current and Motor Constant

When to Use This Method

Use this for:

• DC motors
• Brushless DC motors
• Servo motors
• Control and automation systems

Formula Used

Torque (Nm) = Motor Constant (Kt) × Current (A)

The calculator:

• Converts current units (A or mA)
• Converts motor constant units
• Calculates torque directly

Example

• Current: 10 A
• Motor constant: 0.5 Nm/A

Torque = 5 Nm

This method is ideal when working with motor drivers and controllers.

Understanding the Torque Results

After calculation, the tool shows:

• Torque in Nm
• Torque in lb-ft
• Torque in kg-m

It also provides a plain-language interpretation, such as:

• Very low torque for small precision motors
• Low torque for appliances and fans
• Moderate torque for industrial equipment
• High torque for heavy machinery
• Very high torque for vehicles and large systems

This makes the result useful even if you are not an engineer.

Motor Type Reference Explained

The calculator lets you select a motor type for context. This does not change the math, but it improves the interpretation.

Here is what each type generally means:

• AC Induction Motor
  Reliable, efficient, and common in industry
• Brushless DC Motor
  High efficiency, low maintenance, good speed control
• Brushed DC Motor
  Simple and low cost, but requires maintenance
• Stepper Motor
  Precise positioning, lower torque at high speed
• Servo Motor
  Excellent control of position, speed, and torque
• Synchronous Motor
  Constant speed, used where timing matters

Common Mistakes When Calculating Motor Torque

Avoid these errors:

• Ignoring efficiency
• Using RPM directly without conversion
• Mixing units
• Assuming rated torque equals starting torque
• Oversizing or undersizing the motor

The calculator helps prevent these mistakes by handling conversions automatically.

When to Use a Torque Calculator

This tool is useful for:

• Motor selection
• System design
• Troubleshooting
• Education and training
• Cost optimization
• Preventing mechanical failure

It saves time and reduces guesswork.