3D Printing Calculators

FDM calibration & firmware

Klipper Rotation Distance Calculator

Klipper does not use e-steps. It uses millimetres of filament per motor revolution. Calibrate with requested vs actual length, or convert an old M92 E value with the stepper geometry.

Inputs

Units
mm

Value already in printer.cfg. Typical BMG-class ~22.68 mm; un-geared ~33–40.

mm
mm

If actual is short, rotation_distance is too large — the calibrated value will drop.

200 for 1.8° motors, 400 for 0.9°.

steps/mm

M92 E. Used only for the from-e-steps conversion, but always calculated.

Driven/driving teeth. Dual-drive BMG clones are often ~3:1 — check the wiki, then measure.

Results

rotation_distance to use
21.5441mm

Follows the mode dropdown.

From e-steps
34.4086mm
From measured lengths
21.5441mm

Recommended gear

Calculation method

Calibration: new rotation_distance = old × actual / requested. If the printer pushed only 95 mm when asked for 100 mm, rotation_distance was too high and must fall (the opposite of Marlin e-steps, which rise). From e-steps: rotation_distance = (full_steps_per_rev × microsteps × gear_ratio) / e_steps. Both numbers are always computed; the highlighted result follows the mode select. Lengths are millimetres. Invalid when any of requested, actual, e-steps, steps, microsteps or gear ratio is not positive.

Exact formula

new_rd = old_rd × actual / requested (too little extruded → smaller RD). from_esteps = (full_steps × microsteps × gear_ratio) / e_steps. The live output follows the mode dropdown; both results are always computed. Limits: Gear ratio must match the physical extruder; calibrate hot. The dropdown only picks which of the two always-computed results is primary.

Save it in printer.cfg

Under the extruder section: rotation_distance: the number this page gives. Then reprint the 100 mm test.

Frequently asked questions

Why is this the inverse of e-steps?

E-steps are pulses per millimetre. Rotation_distance is millimetres per revolution. More pulses/mm means fewer millimetres per turn.

Do I still set pressure advance after this?

Yes. Rotation_distance is the hardware millimetres. PA and slicer flow are separate.

What gear ratio for a BMG clone?

Many are 50:17 ≈ 2.94, but clones wander. Convert from e-steps only as a first guess, then run the 100 mm test.

Should I disconnect the hotend?

Follow your firmware guide. Measuring with melt pressure in the way under-reports actual length.

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