How to use it
- Choose the step angle of the motor: 1.8° is the most common, 0.9° for finer motion.
- Choose the microstepping set on the driver (jumpers or firmware), for example 1/16.
- Choose Belt and pulley and enter the belt pitch (2 mm for GT2) and the number of pulley teeth, or Lead screw and enter its lead.
- Enter a feed speed to see the pulse frequency and rpm. Copy the steps per mm into your firmware (for example the steps-per-unit setting in Marlin or Klipper’s rotation distance, which is the travel per revolution).
Formulas
- Microsteps per revolution = (360° / step angle) × microstepping
- Travel per revolution = belt pitch × pulley teeth, or the screw lead
- Steps per mm = microsteps per revolution / travel per revolution
- Travel per microstep = 1000 / steps per mm (µm)
- Step frequency = steps per mm × speed (Hz); motor rpm = speed / travel per revolution × 60
Worked example
A 3D printer axis with a 1.8° motor, 1/16 microstepping, GT2 belt (2 mm) and a 20-tooth pulley: 200 × 16 = 3200 microsteps per revolution, 2 × 20 = 40 mm per revolution, so 80 steps/mm, and each microstep moves 12.5 µm. At 50 mm/s the driver needs 80 × 50 = 4000 Hz and the motor turns at 50 / 40 × 60 = 75 rpm.
The Z axis with a T8 lead screw (8 mm lead) at 1/16: 3200 / 8 = 400 steps/mm, 2.5 µm per microstep.
Tips
- Calibrate after calculating. Move 100 mm, measure, and scale the steps per mm by commanded / measured distance if the belt or screw is not exactly nominal.
- Pitch vs lead: multi-start screws move several pitches per turn. Always enter the lead.
- Gearboxes: for a geared motor, multiply the steps per revolution by the gear ratio before using the calculator (or divide the travel by it).