Steps per mm Calculator

In short Steps per millimetre tells the firmware how many motor steps move an axis one millimetre, and for belt and lead-screw axes it is pure geometry rather than something to tune. A belt axis is the motor steps per revolution times the microstepping, divided by the pulley circumference — and the circumference of a toothed pulley is simply teeth times belt pitch, with no π involved, because the belt engages tooth by tooth. A 200-step motor at 16× on a 20-tooth GT2 pulley gives exactly 80 steps/mm, which is why nearly every X and Y axis in existence is set to that. A lead screw is the same numerator over the LEAD, and this is where the common mistake lives: the usual T8 screw has a 2 mm pitch and four starts, so it advances 8 mm per revolution. Its lead is 8 mm, not 2, and using the pitch produces a Z axis that moves four times too far. With 8 mm and 16× microstepping you get exactly 400 steps/mm. Because both are geometric, they should not need calibrating. If X or Y is measurably out, the cause is mechanical — a slipping pulley grub screw, a loose belt, or the wrong pulley — and adjusting steps per millimetre to hide it makes the error move around instead of going away. The extruder is the exception, and the only one: how far filament advances depends on how the drive gear grips it, so E steps are calibrated by measurement. Mark the filament further up than you intend to extrude, extrude slowly, and measure what is left.