# Stepper Motor Calculations

IPM = (Frequency * 60) / (Turns Per Inch * Steps Per Revolution * Microsteps)

Configuring software steps per unit:

This variable stores how many steps to take to move the X axis 1 inch. You will need to set this as accurately as possible if you want your machine to be accurate. There are two ways to set it:

- Move and Measure - slap a pen or marker on as a tool head and draw a 1000 step line. Measure it and divide 1000 by the length in inches.
- Calculate Step Size - this one is the preferred way of doing things. Its rather easy to calculate step size based on your drive mechanism.

For threaded rod type drive systems:

Find your TPI (Turns Per Inch). for example, 1/4"-20 threaded rod means that there are 20 threads per inch single start (aka 20 turns = 1 inch.) Simply take that number and multiply it by the steps in a revolution. With a 400 step motor (200 steps per revolution at half step), it would be 8000 steps per inch.

For belt/pulley systems:

- Find the circumference of your drive pulley. (remember circumference = 2*pi*r) (say: 2.75")
- Calculate step size (ie: circumference / steps per revolution) (say: 2.75" / 400 = 0.00625")
- Divide 1 inch by step size (1" / 0.00625" = 160 steps/inch)