steps_per_mm = (motor steps-per-rev × microstepping) ÷ travel-per-motor-rev. For a belt drive: travel-per-rev = pulley teeth × belt pitch. Example: a 1.8° motor (200 steps/rev) at 1/16 microstepping with a 20-tooth GT2 pulley (2 mm pitch → 40 mm/rev) gives (200 × 16) ÷ 40 = 80 steps/mm.
For a leadscrew, travel-per-rev is the screw lead (e.g. 8 mm for a common T8), so (200 × 16) ÷ 8 = 400 steps/mm. Set it in your firmware, then calibrate: command a 100 mm move, measure the actual distance, and scale: new = old × (commanded ÷ measured). Do it for every axis; the two towers should match.
For a leadscrew, travel-per-rev is the screw lead (e.g. 8 mm for a common T8), so (200 × 16) ÷ 8 = 400 steps/mm. Set it in your firmware, then calibrate: command a 100 mm move, measure the actual distance, and scale: new = old × (commanded ÷ measured). Do it for every axis; the two towers should match.