# Steps per mm calculator

URL: https://www.clove3d.com/tools/steps-per-mm/

Calculate steps/mm (and steps/degree) for stepper motor axes on CNC machines and 3D printers. Supports leadscrews, GT2 and GT3 timing belts, and rack & pinion drives. Outputs copy-ready GRBL and Marlin firmware configuration lines.

## Formula

steps_per_mm = (steps_per_rev x microstepping) / lead_mm

For belts:      lead_mm = belt_pitch_mm x pulley_tooth_count
For leadscrews: lead_mm = pitch_mm x thread_starts
For rack & pinion: lead_mm = pi x module x pinion_tooth_count

## Inputs

- Drive type: leadscrew, belt, or rack & pinion
- Motor full steps per revolution (200 for 1.8 deg, 400 for 0.9 deg)
- Microstepping setting (1, 2, 4, 8, 16, 32...)
- Drive-specific parameters (pitch and starts for leadscrews; belt pitch and pulley teeth for belts; module and teeth for rack & pinion)

## Outputs

- Steps per mm value
- GRBL config line: $100=<value> (X axis), $101= (Y), $102= (Z)
- Marlin config line: DEFAULT_AXIS_STEPS_PER_UNIT

## Key facts

- GT2 belt pitch is 2 mm; GT3 belt pitch is 3 mm.
- Leadscrew lead = pitch x starts. A T8 4-start with 2 mm pitch has 8 mm lead per revolution.
- Microstepping above 16x improves low-speed smoothness but does not increase positioning accuracy on most drivers.
- Always calibrate steps/mm from the hardware spec, not by measuring prints (print measurement conflates steps/mm with extrusion and shrinkage errors).

## FAQ

Q: Why does steps/mm matter so much?
A: A 1% error in steps/mm compounds over distance. On a 200 mm move that is 2 mm of dimensional error. Correct steps/mm is the foundation of dimensional accuracy on any motion-control machine.

Q: What is the difference between pitch and lead on a leadscrew?
A: Pitch is the distance between thread crests. Lead is how far the nut travels per full revolution. For a single-start thread they are equal. For a 4-start T8 rod with 2 mm pitch, the lead is 8 mm.