Pololu Robotics & Electronics
My account Comments or questions? About Pololu Contact Ordering information Distributors

Pololu Forum

How to calculate linear force

I want to use a 20D or 25D motor to operate a lead screw. Is there somebody here who can tell me how to convert the torque of the motor to ounces of linear force?


When you are using a lead screw, the conversion from torque to linear force is more complicated than a simple wheel or lever arm (which is what is described in our Force and Torque blog post). You will need to take into account the pitch diameter, thread density, and coefficient of friction of the lead screw. Additionally, the weight of the load could be opposing or assisting the direction of travel depending on if you are raising or lowering it (unless your leadscrew is mounted in a strictly horizontal orientation).

You can find a breakdown of the calculations in the “Mechanics” heading of this Wikipedia entry for Leadscrew. Additionally, there are some online calculators available that you might find helpful, like this one from Daycounter