How to Measure Brushless Motor and Propeller Efficiency

By Charles Blouin

Video Tutorial

Testing your motors and propellers is the most effective way to evaluate performance and find areas for improvement in your design.

It allows you to make improvements in efficiency, which translates directly into increases in endurance, flight time, payload capacity, and more.

In this article we will cover both the how and the why of motor and propeller testing.

Table of Contents

  1. Why Test Your Motors and Propellers
  2. What Parameters Should I Measure?
    1. Brushless motor efficiency
    2. Propeller efficiency
    3. Overall system efficiency
  3. How to Test Motors and Propellers with a Thrust Stand
  4. Test Procedure for Static Tests
  5. How to Use the Efficiency Results

Why Test Your Motors and Propellers

You must first ask yourself, what are your, or your end user’s needs? This question is important as it will help you know which parameters to optimize. 

  • Do you want to fly longer to film uninterrupted for longer periods?
  • Do you want to carry a larger payload?
  • Do you need more thrust and power to go faster, or to improve handling in strong winds?
  • Do you have overheating problems and your application requires you to minimize failure rate?

The final choice of power system depends not only on the airframe and payload, but also on your application.

What Parameters Should I Measure?

Brushless Motor Efficiency

NTM propdrive 35-30 brushless motor and Quantum 13-4 carbon fiber prop

Figure 1: NTM propdrive 35-30 brushless motor and Quantum 13-4 carbon fiber prop.

To fully characterize a motor and determine its efficiency, you need to measure the following parameters.

  • Voltage (V)
  • Current (A)
  • Throttle input (%)
  • Motor load or torque (Nm)
  • Speed (RPM)

The parameters listed above are important because they allow you to determine the following key performance indicators:

  • Mechanical power (Watts) = Torque (Nm) * Speed (rad/s)
  • Electrical power (Watts) = Voltage (V) * Current (A)
  • Motor Efficiency = Mechanical power / Electrical power

The output speed is a function of the throttle, in %, and of the load or torque, in Nm. If you want to completely characterize a motor, you will need to test it with multiple input voltages and different loads. The throttle is changed with the controller, and the load is changed with the type and size of propeller.

Further reading: How Brushless Motors Work and How to Test Them

Propeller Efficiency

To find propeller efficiency, you will need to measure the following parameters:

  • Speed (RPM)
  • Torque (Nm)
  • Thrust (g)

These parameters allow you to determine:

  • Mechanical power (Watts) = Torque (Nm) * Speed (rad/s) ← same as the motor
  • Propeller efficiency (g/watt) = Thrust (g) / Mechanical power (Watts)

Note that the mechanical power is the same for the motor and propeller. That is because all the motor’s mechanical power output goes into the propeller, since it is directly coupled to the motor’s shaft.

Overall System Efficiency

The overall efficiency of your system depends on how well your motor and propeller work together. Even with a motor and propeller that are highly efficient on their own, your system can be very inefficient if the two parts don’t match well.

Because these parts have a common link (the shaft), the overall system efficiency is expressed as:

System efficiency (g/watt) = Propeller efficiency (g/watt) * Motor Efficiency

where the system efficiency is in grams per watt of electrical power. Changing the motor, propeller, or even switching to another ESC will all contribute to changing the system efficiency.

Moreover, the efficiency value will only be valid for a specific command input and mechanical load. In practice, this means that you will need to test your motor over a range of command inputs and with various propellers (to vary the mechanical load) in order to get a full efficiency characterization.


How to Test Motors and Propellers with a Thrust Stand

In summary, to obtain motor and propeller efficiency you need to simultaneously record voltage, current, torque, thrust, and motor speed. By combining these readings you can extract the electrical and mechanical power, which in turn will give you the efficiency values.

The easiest and most effective way to perform these tests is with a thrust stand, a piece of equipment specifically designed for characterizing motors and propellers.

We used the Series 1585 thrust stand (5 kgf/ 2 Nm) to collect the data discussed below, but we also offer thrust stands measuring up to 500 kgf.

Further reading: Why You Should Test Your Drone's Motors and Propellers

Series 1585 test stand

Figure 2: The Series 1585 thrust stand with brushless motor and propeller

Test Procedure for Static Tests

In this article we will only cover static tests (we won’t talk about dynamic tests involving angular acceleration, estimating stall torque, etc…).

Before starting your tests, we recommend to:

  • Install your propeller in pusher configuration, to reduce ground effects with the motor mounting plate
  • Have a reasonable distance between the propeller and other objects, again, to avoid ground effects
  • Have all safety measures in place to protect the people in the room
  • Configure your thrust stand to automatically cutoff the system should any parameter exceed its safe limit

A simple but effective test consists of ramping up the throttle in small steps, and recording a sample after every step. Before taking the sample at each step, allow the system to stabilize for a few seconds.


In the video at the beginning of the article, we demonstrate how we manually varied the throttle from 0 to 100% in 10 steps. This procedure could also have been performed using the RCbenchmark software’s automated test feature, which is covered in another tutorial.

Further reading: Automated Propulsion Test Scripts for Your Drone

The results obtained from our manual step test are shown in this CSV file.

brushless motor test stand

How to Use the Efficiency Results

You can analyze your output data using any plotting software. Below is an example of a plot we generated obtained using the data from the CSV file linked above.

Here we have compared propeller thrust and mechanical efficiency, to see at what points our propulsion system operates most efficiently.


propeller thrust graph

You could then compare this data with data from other tests using the same protocol but different propellers to find the one that is most efficient with your motor.

For more examples of the types of analysis that you can do with this data, check out our articles on motor and propeller testing.


In conclusion, with the right equipment it is easy to obtain meaningful data that will allow you to measure brushless motor and propeller efficiency.
You can use this data to make informed design decisions and improve the performance of your UAV.

If you'd like to start testing your own motors and propellers, check out our thrust stands and don't hesitate to contact us for more information:

Liked this tutorial or have comments? Let us know below.

15 Responses

Lauren Nagel

November 27, 2023

Hi Daniel,
Great question. In this case the motor efficiency calculated is actually the motor + ESC efficiency. The system efficiency reflects the efficiency of the whole system including the motor, propeller, and ESC.
- Lauren from Tyto Robotics

Daniel Lee

November 27, 2023

Is efficiency of the ESC/inverter included in the system efficiency calculation? Or should it be?

Lauren Nagel

August 07, 2023

Hi Selçuk, thank you for your question! The Series 1585 thrust stand can be purchased directly on our website here:
The current price is $1,075 USD

Selçuk GÜL

August 07, 2023

As a model club in Turkey, we want to measure the performance of our engines. How can we buy this product. And may we know the price?

Lauren Nagel

May 10, 2022

Hi Anya,
Thanks for your question. The cut-off values are meant to prevent you from drawing excessive power and burning out your motor or ESC. You can get a rough idea of a safe operating range from the specifications provided by the manufacturer of your battery and motor. This video may help you set your cut-off values (start at 3:30), and if you need any more help feel free to send us an email:


May 10, 2022


I am new to this and I am doing a project on propellers using thrust rig 1580 model.
I am confused about how to set the cutoff values.
I am using “overlander batteries of 2200mAh capacity (11.1v 3s)” and “Propdrive 28-30s 800KV” 12 poles motor.


Lauren Nagel - RCbenchmark staff

April 27, 2021

Hi Shane,
Thanks for your comment! Your problem sounds like just the type of frustration our products were designed to solve. The prices for our smaller products can be found in our online store (, but if you need a larger test stand (>5kgf), send an email to our sales specialist Joffrey ( and he can set you up with a quote.

Shane Anderson

April 27, 2021

Well done…i am so frustrated by lack of motor data. Your product may just suit me. Is it affordable?


Charles Blouin -RCbenchmark staff

February 22, 2021

@Ashmita Unfortunately, the correlation between throttle (in%) and voltage is not well defined. It can change depending on the firmware and the ESC manufacturer. You can try a linear approximation, but that is usually off.

Charles Blouin (RCbenchmark)

February 22, 2021

Hello! @John: You are right that the efficiency of the propeller changes with the wind speed. Static tests will provide the propeller efficiency at hover. For dynamic testing, you can use a wind tunnel such as the one we offer, or test on a moving vehicle (we have an article about that here:


February 22, 2021

Generally, static tests do not provide efficiency for the propeller. It’s confusing to denote “propeller efficiency”, it should not be defined for such tests.


February 22, 2021

Hoe to calculate thrust and torque of the BLDC Motor?


February 22, 2021

Let’s say we only know the PWM signal input to the ESC, how do we calculate the throttle percentage from this information? I would like to finally note the input voltage to the motor after the ESC.

Joffrey Ferry - RCbenchmark staff

September 30, 2020

Hi Santanu!

The mechanical power (output power) is measured by multiplying the torque with your motor’s rotation speed (mech. power = torque x RPM).

The motor efficiency is the mechanical power divided my the electrical power (motor eff. = mech. power / elec. power).

The propeller efficiency (kgf/W) can be calculated by dividing the thrust by the mechanical power (propeller eff. = Thrust / mech. power).

Both thrust and torque are measured by the stand’s load cells.

santanu mondal

September 29, 2020

How to measure output power and efficiency of the BLDC motor?

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