Elegoo Neptune 4 / 4 Pro extrusion calibration (rotation_distance)

The stock Elegoo Neptune 4 / 4 Pro rotation_distance is 28.7086 mm per revolution. That is the starting point in its Klipper config — tune it once with the mark-and-measure test and the extruder tracks reality. The rotation distance & e-steps calculator does the correction math and prints the exact line to paste; the full calibration guide explains the test in detail.

The Neptune 4 family ships with Elegoo’s Klipper fork, and the stock extruder config pairs rotation_distance 28.7086 with a 52:10 gear ratio — the 5.2:1 reduction is why the number sits above 28. This default is a community-verified value consistent with the stock config — manufacturers revise hardware without notice, so treat it as the starting point the calibration test then refines. Source.

How to calibrate on the Elegoo Neptune 4 / 4 Pro

1. Heat the hotend to normal print temperature and mark the filament exactly 120 mm above the extruder inlet with a ruler and a fine marker or tape flag.
2. Extrude 100 mm slowly. From a console send G91, then G1 E100 F60 — slow, so back-pressure does not skew the measurement. If Klipper rejects the move, set max_extrude_only_distance to at least 101 under [extruder] and RESTART first.
3. Measure what actually went through. Measure from the inlet to the mark again — actual extrusion is 120 − remainder (23 mm remaining means 97 mm extruded).
4. Compute the new value. new rotation_distance = old × actual ÷ requested — with the stock 28.7086 and 97 mm measured: 28.7086 × 97 ÷ 100 = 27.8473. Note the direction: under-extrusion pushes rotation_distance down. The calculator does this arithmetic for you.
5. Save in printer.cfg. Paste rotation_distance: 27.8473 under [extruder] (leave gear_ratio: 52:10 as it is), then RESTART. Klipper has no M500 — the config file is the save.
6. Confirm. Repeat the test once; the mark should land 20 mm from the inlet. Within about ±0.5 mm is measurement noise, not a reason to iterate.

Notes for the Elegoo Neptune 4 / 4 Pro

This value is community-verified against the stock Elegoo config. Keep the gear_ratio line untouched when you change rotation_distance — Klipper applies the ratio on top, and editing both doubles the correction.