Hi

how do one determine what stepper motor size to use for a build?

Is the any formula or any other way to measure to figure out what size of
stepper motor to use

Cory

I would also like to know. I would like to run a three axis gantry router table with the intent of cutting parts out of 3/4 inch medite , mdf, plywood, using carbide routerbits mostly 5/8 or 3/4 '' wide on mach 2. I was looking at some motors on ebay, which were nema 23 500oz/inch. using these as a marker would they be right for the job, not enough or overkill?

Most stepper motor manufacturers have software to assist you in choosing the correct size steppers. It's not necessarily a simple task, depending on your math skills.
http://www.danahermotion.com/design_tools/sizing_selection.php
http://www.orientalmotor.com/support/product_recommend.htm