Stepper Motor Steps per mm Calculator (3D Printer / CNC)
Steps per millimetre for belt-driven and leadscrew axes and for extruders — motor step angle, microstepping, pulley teeth and belt pitch or screw lead, gear ratio — with resolution and the calibration correction formula.
How it works
Belt: steps/mm = (360/step angle × microsteps × gear ratio) ÷ (belt pitch × pulley teeth). Screw: ÷ lead. Extruder: ÷ (π × hob diameter). Corrected = current × commanded ÷ measured
Firmware needs to know how many step pulses move an axis one millimetre, and the number follows from the mechanics: a 1.8° motor makes 200 full steps per turn, the driver subdivides each into microsteps, any gearbox multiplies the count, and one motor turn moves the axis by the belt pitch times pulley teeth (40 mm for a GT2 20-tooth pulley) or by the screw lead. Hence the familiar 80 steps/mm for belt axes and 400 for T8 leadscrews at 1/16 microstepping. Extruders use the circumference of the hobbed drive gear, and geared extruders multiply accordingly. Real machines deviate slightly — belt stretch, gear tolerance, filament slip — so the final value is calibrated by commanding 100 mm, measuring the true travel and scaling.
Worked example
GT2 belt on a 20-tooth pulley, 1.8° motor at 1/16 microstepping: 3,200 steps per 40 mm = 80 steps/mm, 12.5 µm per microstep (200 µm per full step).
Frequently asked questions
Does more microstepping improve accuracy?
It smooths motion and reduces noise, but positional accuracy is limited to roughly the full-step resolution because microstep torque is tiny. 1/16 is the practical norm.
Why is my extruder value different after changing filament?
Different filament diameters and hardness grip the hobbed gear differently. Calibrate e-steps with the filament you use most, and rely on flow % for fine tuning.
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This calculator is for educational purposes. Double-check important results before acting on them.