Steps per mm Calculator

Every motor move on a printer or CNC is a whole number of tiny steps, and steps per mm is how many of them make the axis travel one millimeter. Get it right and a commanded 100 mm move is exactly 100. This works it out from the drive for a belt or lead-screw axis, and corrects your extruder E-steps from a quick measured test.

Belts and screws are pure geometry

For a belted axis, one motor turn moves the belt by the pulley's tooth count times the belt pitch, so steps per mm is the motor's steps per turn times the microstepping, divided by that travel. A standard 200-step motor at 16 microsteps on a GT2 belt and a 20-tooth pulley gives exactly 80 steps per mm, which is why that number shows up on so many printers. A lead screw is the same idea with the screw's lead in place of the belt travel, so a common Z comes to 400.

The extruder is the one you measure

You cannot calculate extruder steps the same way, because the filament is gripped by a hobbed gear and slips a little, and the real grip diameter is never exactly nominal. So you calibrate it. Mark the filament 120 mm above the extruder, tell the printer to push 100 mm, then measure how far the mark actually moved. If it fed only 95, the extruder is under by 5 percent, and the new E-steps is the old value times 100 divided by 95.

Microstepping multiplies the count, not the travel

Microstepping splits each full motor step into smaller ones for smoothness, so it multiplies steps per mm without changing how far the axis goes. Going from 16 to 32 microsteps doubles the steps-per-mm number. It buys quieter, finer motion but not real accuracy, which is set by the belt or screw. Match the microstepping value here to what your driver is actually set to, or the number will be off by that factor.

Prove it after you set it

A calculated or calibrated number is a starting point until the machine confirms it. After you enter steps per mm, command a known move, 100 mm on an axis or 100 mm of extrusion, and measure the result. If it is off, feed the measured value back in. One or two rounds lands it. This is the difference between a printer that holds dimensions and one that is always a hair short or long.

More MakerKiln tools

• print cost3D Print Cost CalculatorFilament, power and wear cost of a print, with a price to charge.→
• pulley rpmPulley RPM CalculatorOutput RPM, drive ratio and torque change between two pulleys.→
• stepper vrefStepper Driver VREFThe VREF voltage to set a stepper driver's current for your motor.→

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