Step-by-Step Motor Torque Calculation: Practical Examples for Micro DC Motors Selection

May 21, 2025
Annie

Have you ever struggled with underpowered devices or selecting the wrong motor? Understanding torque is the first step to precisely matching a motor to its load. Here, we’ll start by unpacking the fundamental formula: Torque = 9550 × Power / RPM. More than just a calculation tool, it is the key to understanding the critical balance between a motor’s force, speed, and efficiency. In the following sections, we will break down the physics behind this formula, explore how each parameter affects performance, and show you how to use it to select the perfect “heart” for your project.

Key Takeaways

Use the formula Motor Torque = 9550 × Power / RPM to calculate the torque a motor can deliver. This helps ensure you select the right motor for your project.
Always check the power and speed ratings on the motor’s datasheet. Accurate values are crucial for correct torque calculations.
Consider the gear ratio when calculating torque. A higher gear ratio increases output torque, which is essential for applications needing more force.
Match the motor torque to the load requirements. This prevents overheating and mechanical failure, ensuring your device operates efficiently.
Consult with experts like INEED for tailored motor solutions. They can help you choose the right motor based on your specific torque and application needs.

What Is Motor Torque

Definition And Importance

Motor torque measures the force that causes an object to rotate. When you use a motor, torque tells you how much twisting force the motor can deliver to move or lift something. You see torque in action every time you open a door or ride a bike. In motors, torque is the key to making machines work. If you want your device to move quickly or handle heavy loads, you need enough torque.

Accurate motor torque calculation matters for every project. You must know how much force your motor can produce. High torque lets machines like extruders and servo presses apply strong forces. This means your equipment can work faster and respond quickly. When you calculate torque correctly, you avoid problems like overheating or mechanical failure. You also make sure your motor matches the needs of your application.

Tip: Always check the torque requirements before choosing a motor. This helps you avoid costly mistakes and keeps your machines running smoothly.

Electric Motor Torque In Applications

Electric motor torque plays a big role in many industries. You use electric motor torque to control robots, run conveyor belts, and power medical devices. In robotics, electric motor torque helps arms lift objects and move with precision. In manufacturing, electric motor torque allows machines to press, cut, or shape materials with speed and accuracy.

You also see electric motor torque in everyday products. Smart locks need enough torque to turn locking mechanisms reliably. Pool cleaners use electric motor torque to climb stairs and remove debris. Land survey instruments rely on electric motor torque for precise movement and measurement. When you select a motor, you must consider how much electric motor torque your application needs. This ensures your device works efficiently and lasts longer.

Application	Why Torque Matters
Robotics	Precise movement, lifting
Smart Locks	Reliable locking/unlocking
Pool Cleaners	Climbing, debris removal
Survey Instruments	Accurate positioning

Motor Torque Calculation Steps

Identify Power And Speed

You must start every motor torque calculation by identifying two key values: power and speed. Power tells you how much work the motor can do. Speed, measured in revolutions per minute (RPM), shows how fast the motor shaft turns. You can usually find these values on the motor’s datasheet or label.

For example, if you use a planetary gear motor from INEED, you might see a power rating of 10 watts and a speed of 100 RPM. Spur gear motors and worm gear motors also display these values clearly. Always check the voltage and current requirements. DC servo motors often run at 24VDC or 48VDC and need stable voltage and enough current for safe operation.

Here is a table showing typical power ranges for motors used in automation and robotics:

Motor Type	Power Range
High-precision servomotors	10W to 3 kW
Customized solutions	100W to 100 kW

Note: Incorrect probing or poor connections can lead to errors when you identify power and speed. Make sure your measurements are accurate to avoid mistakes in your torque calculations.

Apply The Motor Torque Formula

Once you have power and speed, you can use the motor torque formula. The most common formula for electric motors is:

Motor Torque (Nm) = 9550 × Power (kW) / Speed (RPM)

Power must be in kilowatts (kW).
Speed must be in revolutions per minute (RPM).
The result gives you torque in Newton meters (Nm).

You can use this formula for any motor gearbox, including planetary gear motors, spur gear motors, and worm gear motors. The formula helps you calculate torque quickly and accurately. Always double-check your units before you start the calculation.

Tip: If you use a motor gearbox, remember that the output speed and torque will change based on the gear ratio. Gearboxes reduce speed and increase torque, which is important for applications that need more force.

Calculate Electric Motor Torque Example

Let’s walk through a real example using an INEED planetary gear motor. Suppose you have a motor with these specifications:

Power: 20 watts (0.02 kW)
Speed: 100 RPM

Follow these steps to calculate electric motor torque:

Convert power to kilowatts: 20 W ÷ 1000 = 0.02 kW.
Use the motor torque formula:
Motor Torque = 9550 × 0.02 / 100 = 1.91 Nm.

This means your planetary gear motor can deliver 1.91 Newton meters of torque at 100 RPM.

Now, imagine you use a spur gear motor with a power of 15 watts (0.015 kW) and a speed of 200 RPM. Plug these values into the formula:

Motor Torque = 9550 × 0.015 / 200 = 0.716 Nm.

For a worm gear motor, suppose you have 10 watts (0.01 kW) and 50 RPM:

Motor Torque = 9550 × 0.01 / 50 = 1.91 Nm.

You can see how different motor gearbox types and speeds affect the torque output. Always use the correct values for your application.

Remember: Each motor gearbox, whether planetary, spur, or worm, changes the output torque and speed. Always check the gear ratio and adjust your calculation if needed.

If you want to calculate torque for a custom application, follow these steps:

Identify the power and speed from the motor’s datasheet.
Convert power to kilowatts if needed.
Use the motor torque formula.
Adjust for the gear ratio if your motor uses a gearbox.
Double-check your results for accuracy.

By following these steps, you can perform motor torque calculation for any project. This process helps you select the right motor gearbox and ensures your device works safely and efficiently.

Factors Affecting Motor Torque

Efficiency And Gear Ratios

You must understand how efficiency and gear ratios influence motor torque. Efficiency shows how much input energy becomes useful work. If your motor runs at high efficiency, you get more torque for the same amount of power. Losses from friction, heat, or poor lubrication reduce efficiency and lower the torque output.

Gear ratios play a major role in torque adjustment. When you use a higher gear ratio, you increase the output torque. The relationship is simple:

A higher gear ratio results in increased output torque.
Output Torque = Input Torque × Gear Ratio.
For example, if your input torque is 1 Nm and the gear ratio is 3:1, the output torque becomes 3 Nm.
Gear reduction allows you to move heavier objects by trading speed for torque.

You should select the right gear ratio for your application. If you need more force, choose a higher gear ratio. If you want more speed, use a lower gear ratio.

Load And Safety Factor

Load changes affect the torque your motor must deliver. When the load increases, your motor needs more torque to keep working efficiently. If the load drops, the required torque decreases. You must match your motor torque to the load for stable operation.

Load variations require you to adjust torque for efficient performance.
Motors generate torque based on the load they handle.
Changes in load influence energy efficiency and stability.
Proper motor design for specific operating points improves energy use, especially when loads vary.

Always consider a safety factor when you select a motor. The safety factor helps you avoid overload and ensures your motor lasts longer.

INEED Gear Motor Solutions

INEED specializes in customizing gear motors for optimal torque across many industries. You can choose from planetary gear motors, spur gear motors, or worm gear motors. Each type offers unique benefits for different applications. INEED works with you to design motors that match your torque needs, efficiency goals, and load requirements. You get reliable solutions for robotics, smart locks, pool cleaners, and medical devices. INEED’s expertise helps you achieve the best motor torque for your project.

Real-World Applications And Mistakes To Avoid

Calculate Torque For INEED Motors

You can see how motor torque calculations work in real-world devices. For example, smart locks use a spur gear motor from INEED. You start by checking the power and speed on the datasheet. You then use the torque formula to find the output torque. If your smart lock needs to turn a heavy bolt, you select a gear ratio that increases output torque. Pool cleaners use brushless planetary gear motors. You calculate the output torque to make sure the cleaner can climb stairs and remove debris. Land survey instruments rely on planetary gear motors for precise movement. You use the torque formula to match the output torque to the weight of the instrument and the speed needed for accurate measurements.

Application	INEED Motor Type	Power (W)	Speed (RPM)	Output Torque Calculation
Smart Lock	Spur Gear Motor	15	200	0.716 Nm
Pool Cleaner	Brushless Planetary	20	100	1.91 Nm
Survey Instrument	Planetary Gear Motor	10	50	1.91 Nm

Tip: Always use the correct torque formula and check the gear ratio to get the right output torque for your application.

Common Calculation Errors

You can avoid many mistakes by following best practices. Here are some common errors and how to prevent them:

You forget to factor in vibration. This can shorten the life of your motor and reduce output torque.
You skip regular lubrication. Motors that make short, precise movements need full lubrication to prevent sticking and loss of output torque.
You ignore thermal performance. If you do not understand how heat affects your motor, you may select the wrong power level and lose output torque during long cycles.
You use the wrong units in the torque formula. Always check that power is in kilowatts and speed is in RPM.
You overlook the gear ratio. This leads to incorrect output torque calculations.

Note: You should always double-check your calculations and consider environmental factors to ensure accurate output torque.

Selecting The Right Motor

You need to match the output torque to your application. The continuous torque capability of your motor must be higher than the RMS torque requirement. This prevents thermal overload and keeps your device running safely. You should also consider power needs, gearbox efficiency, and safety margins. INEED’s technical support helps you choose the right motor. You get recommendations based on load, duty cycle, and dynamic parameters. You limit the output torque to the maximum allowed for your system. You use low speeds during commissioning to avoid damage.

Aspect	Details
Recommendations	INEED provides advice for drive motors and gearboxes.
Considerations	You look at maximum load, average load, and duty cycle.
Torque Limitation	You keep output torque within safe limits for your device.
Emergency Stop Strategy	You use safe stop methods to protect moving parts.
Commissioning	You start at low speeds to avoid errors and damage.

Callout: Always select a motor with output torque that meets or exceeds your calculated needs. This ensures long-term reliability and safety.

You can master motor torque calculation by following these steps:

Check the motor power in watts.
Find the speed in RPM.
Convert RPM to radians per second.
Use the formula T = P / ω to get torque.

Understanding these variables helps you choose the right motor for your needs. INEED offers tools and support to make your calculations easier:

Parameter	Description
T	Torque using T = (I – INL) × (KT × N × h)
Output Power	Speed × Torque × 0.00074 = Output Power [W]

Reach out to INEED for expert advice and technical support.

FAQ

How do you convert motor power from watts to kilowatts?

You divide the power value in watts by 1,000. For example, 500 watts becomes 0.5 kilowatts. Always check your units before using the torque formula.

Why does gear ratio affect motor torque?

Gear ratio multiplies the input torque. If you use a higher gear ratio, you get more output torque but less speed. This helps your motor handle heavier loads.