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:

1. 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.
2. 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:

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

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Steps & Frequency Step Angle: 1.8° Physical Steps Per Revolution: 200 = 360° in a revolution ÷ 1.8° step angle Micro-step Mode: 8th Effective Steps Per Revolution: 1600 = 8 microsteps per step x 200 physical steps per revolution RPM (Revolutions Per Minute): 1000 Steps Per Minute: 3200000 1600 effective steps per revolution x 2000 revolutions per minute Hz (cycles per second): 26666.67 = 3200000 steps per minute ÷ 60 seconds in a minute kHz: 26.7 Hz ÷ 1000 IPM Lead Screw Threads Per Inch: 10 Number of Starts: 2 Turns Per Inch: 5 10 Threads Per Inch ÷ 2 start, so it takes 5 revolutions to move 1 inch IPM (Inches Per Minute): 200 = 1000 RPM ÷ 5 Revs Per Inch

Source  : http://www.probotix.com/stepper_motor_calculations/