Stepper Motor Steps/mm Calculator

Why This Number Matters

Steps/mm (sometimes written as an M92 value in Marlin-based firmware) is the single number that tells your controller board how many motor steps add up to one millimeter of real-world movement. Get it wrong and every dimension is off by the same percentage — a 100mm calibration cube prints at 98mm or 103mm, holes end up undersized, and threaded parts won't mate, even though the machine seems to be running fine.

How to Use This Calculator

Pick your motor's step angle (1.8° is by far the most common on desktop 3D printers and small CNC machines) and the microstepping your driver is set to. Then choose your drive type: belt-and-pulley for X/Y axes on most machines, or leadscrew for Z axes and some CNC setups. For belt drive, GT2 belt (2mm pitch) with a 20-tooth pulley is the de facto standard on machines like the Ender 3, Prusa, and most Voron builds. For leadscrew, a common example is a T8 screw (8mm pitch) with 4 starts, giving 2mm of travel per full rotation.

How We Calculate It

Total steps per motor revolution = full steps per revolution × microstepping. For belt drive, distance traveled per revolution = belt pitch × pulley tooth count; for leadscrew, it's screw pitch × number of starts. Steps/mm = total steps ÷ distance per revolution. A standard GT2/20-tooth belt setup with a 1.8° motor at 16x microstepping gives (200 × 16) ÷ (2 × 20) = 80 steps/mm — the widely cited reference value for that exact configuration.

A Few Notes

This gives you the theoretical value to start from, not the final calibrated one — belt stretch, pulley grub-screw slippage, and leadscrew backlash all introduce small real-world error that this math can't see. After setting this value in your firmware, print or cut a large calibration object, measure it with calipers, and fine-tune with the standard formula: new steps/mm = old steps/mm × (expected size ÷ measured size).