Do Quick Calculation!

Perform fast calculations with our user-friendly online calculator! Conveniently crunch numbers and solve equations instantly. Ideal for quick math tasks, our tool simplifies your daily computations effortlessly. Try our intuitive calculator for accurate results on the go!

Electric Motor Sizing Calculator

Use our electric motor sizing calculator to find the right motor power, torque, speed, and peak torque for your machine with easy, accurate calculations.

Load Requirement (required)
Don't know the torque? Use Force × Radius (drum/pulley) below.
RPM
Acceleration (optional — leave all 3 blank to skip)
RPM
Use the load speed if starting from rest.
sec
Gearbox (optional — leave blank for direct 1:1 drive)
%
Motor Efficiency (optional — for electrical input power)
%
Adds electrical input power = mechanical output ÷ efficiency.
Check a Candidate Motor (optional)
RPM
N·m
From the manufacturer's torque-speed curve — needed for a definitive peak-torque pass/fail.
Only Load Torque and Load Speed are required. Fill in any of the optional sections above for a more complete sizing check.

Choosing the right motor can feel hard. The wrong size can waste power and money. It can also cause heat, poor work, or early wear, which is why you may also need a Motor Overload Calculator.

Our electric motor sizing calculator makes this job much easier. It helps you find the motor power and torque you need.

The tool uses load torque, speed, inertia, and gear data, similar to a Motor Gearbox Ratio Calculator. It can also check a motor you plan to use.

This makes motor selection faster and more clear. It can help with AC motor and induction motor systems. It can also guide basic DC motor sizing.

Still, final motor design needs real motor data. Always check the motor maker's data sheet before you buy.

Electric Motor Sizing Formula

The main motor sizing formula uses torque and speed.

Motor Power (kW) = Torque (N·m) × Speed (RPM) ÷ 9550

For torque:

Torque (N·m) = 9550 × Power (kW) ÷ Speed (RPM)

For load power:

Load Power = Load Torque × Load Speed ÷ 9550

If the motor must speed up a load, you also need acceleration torque.

Acceleration Torque = J × 2π × ΔN ÷ (60 × t)

Here, J is the rotating inertia. ΔN is the speed change. t is the time to reach that speed.

Then:

Total Torque = Load Torque + Acceleration Torque

If you use a gearbox, the calculator also checks the gear ratio and gear loss.

Motor Power = Load Power ÷ Gearbox Efficiency

The tool can then check the motor's rated power and torque.

This is more useful than using a simple motor size chart alone.

How to Use Online Electric Motor Sizing Calculator

Using the calculator is quick. Just follow these steps.

1. Enter the load torque.

Add the torque your machine needs. Pick the right unit, such as N·m or lb·ft.

2. Enter the load speed.

Add the speed in RPM. This tells the tool how fast the load must run.

3. Add acceleration data.

Enter inertia, speed change, and time if the load must speed up.

4. Add gear data.

Enter the gear ratio and gearbox efficiency if you use a gearbox.

5. Check your motor.

Add motor power, speed, and peak torque. The tool will compare the motor with your needs.

The result can show load power, motor power, motor torque, peak torque, and input power, which can be used with a Motor FLA Calculator.

Example Electric Motor Sizing Calculation

Let's say a machine needs 50 N·m of torque. The load runs at 1,500 RPM.

First, find the load power.

Load Power = 50 × 1500 ÷ 9550

Load Power = 7.85 kW

Now, let's add a gearbox with 95% efficiency.

Motor Power = 7.85 ÷ 0.95

Motor Power = 8.26 kW

So, the motor needs about 8.26 kW of mechanical output.

You would then choose the next suitable motor size. You must also check motor torque and speed.

If the motor must speed up a heavy load, peak torque needs more care. The calculator uses inertia and acceleration time for this check.

Think of it like pushing a cart. A light cart starts fast. A heavy cart needs more force. A motor faces the same kind of task.

Electric Motor Sizing and Related Tools

Motor sizing is only one part of a full motor system. You may also need an electric motor wire size calculator or motor wire sizing calculator. These tools help with conductor needs.

An electric motor breaker size calculator can help with circuit protection. An electric motor current calculator can help estimate motor current.

You may also need an electric motor pulley size calculator for belt drives. An electric motor speed calculator can help with RPM and speed changes.

For larger projects, motor sizing software can help with motor design. It can also support motor control systems and motor testing.

Keep in mind that wire size and breaker size depend on local codes and motor data. The calculator should not replace a qualified electrician or engineer.

Final Verdict

Our electric motor sizing calculator gives you a simple way to size a motor. It uses torque, speed, power, acceleration, and gearbox data.

It can help you compare motor options with less guesswork. It also gives a better starting point than a basic electric motor size chart.

For the best result, check the motor's real torque curve and duty rating. Also check electric motor efficiency and local electric motor standards.

Use the tool to plan your motor choice. Then confirm the final choice with the motor maker's data.

FAQs

How to size a motor?

Start with the load torque and speed. Then find the required power with this formula:

Power (kW) = Torque (N·m) × RPM ÷ 9550

Next, check acceleration torque, gearbox loss, and peak torque.

What size electric motor do I need?

You need a motor that can meet the load's power and torque needs. The motor must also handle the required speed and acceleration.

Our electric motor sizing calculator can help you find these values.

How to calculate motor power?

Use this formula:

Motor Power (kW) = Torque (N·m) × Speed (RPM) ÷ 9550

If a gearbox has loss, divide the load power by gearbox efficiency.

What is motor sizing?

Motor sizing means finding the right motor for a machine. It looks at power, torque, speed, acceleration, and duty.

Good sizing helps the motor work well. It can also help avoid excess heat, wear, and energy waste.