Drive Motor Sizing Tool | RobotShop Community

Drive Motor Sizing

The Drive Motor Sizing Tool is intended to give an idea of the type of drive motor required for your specific robot by taking known values and calculating values required when searching for a motor. DC motors are generally used for continuous rotation drive systems, though can

This is a companion discussion topic for the original entry at

thank you for the drive motor tool. It would be nice to save or print the results in some easy manner. I would like to know how you handle friction at the various locations, generally promotional to weight. I would also recommend a %slope time variable to separate peak power from watt-hrs.

It would be great if it showed you the motor options after.

tell th torque of each motor

The torque for each motor we sell can be found on the product page on

Thank you for this tool! Do the output(for each motor) refer to the free-run and stall torque? Or, are these values for a specific operating point?

The torque value would what is required in that specific situation, and can be considered the maximum continuous torque. Based on observations and what motor manufacturers provide, the stall torque would be ~4x or 5x this value.

Can you tell me why my result is different than yours?

Mass: 25 kg
Motors: 1
Wheel radius: 0.2 m
Velocity: 2 m/s
Incline: 0
Acceleration: 1 m/s2

You get:
Torque = 78 kgf-cm

I get:
Torque = (25 kg) x (1 m/s2) x (0.2 m) x (1/9.8 m/s2) x (100 cm/m) = 51 kgf-cm


@Mitch Berkson Factor in 65% efficiency (that’s the default value), which gives 51 / 0.65 = 78.

Or in this simpler example:

Mass: 1 kg
Motors: 1
Wheel radius: 1 m
Velocity: 0 m/s
Incline: 90
Acceleration: 0 m/s2

I would expect a torque of 9.8 N-m, but the calculator says 15 N-m.

Thanks. The calculator and explanation are so well done that if you’re going to throw in an arbitrary number, it’s a shame not to mention it up front.

Whoa. Now I see that you had efficiency as a parameter. Sorry about that. You can delete any superfluous comments I made.

HI! I was building an Electric Wheelchair. And i calculated the output values required for the motor using this Tool. This tool is very useful. Can you please provide the formulae used in this tool to calculate torque, speed and power? Thanks

@Amit Everything is in the tutorial:

@Coleman Benson I’ve read the tutorial provided, but I have 2 questions regarding the content.

#1 Can you explain in details what does the efficiency value stand for, and where should I look for it.
#2 Why didn’t you account for rolling resistance ?

#1 There are general losses in efficiency: DC brushless motors are not 100% efficienct, nor are the gearing to which they are connected. Batteries are also not 100% efficient, and there are also losses in cabling. The value provided would be a total of these losses. Since none of the parts are known until after choosing the products, we can only estimate a total efficiency.
#2 Honestly for simplicity, but if you can derive a simple equation using the input above, we’d be happy to add it.

Hi. i need information about EMA actuators Application in Mobile Robotics

@Rabea Unless we are missing something, EMA = electro-mechanical, which essentially covers all DC motors?

Dear Coleman Benson
could you send to me your contect

@Rabea For topics related to robotics, I can be reached at [email protected]