Guide · Measurement tools
E-steps and rotation distance after an extruder swap
Why a new extruder needs new E-steps or rotation distance, the values Bondtech publishes, Klipper's mark-and-extrude method, and where it sits in the calibration order.
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Short answer
A new extruder has different gearing, so your firmware needs a new E-steps value (Marlin) or rotation distance (Klipper). Start from the maker's published number, then measure: mark the filament, extrude a fixed length slowly, and scale the value by what actually went in. Do this before pressure advance and before flow tuning.
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Why a new extruder needs new numbers
E-steps tell Marlin how many motor steps push 1 mm of filament. Klipper expresses the same thing the other way round, as rotation distance: millimeters of filament per full motor turn. Both depend on the drive gear size, the gear ratio and the motor's microstepping. Change the extruder and every one of those can change.
Values the makers publish
| Extruder | Published value | Source |
|---|---|---|
| Bondtech BMG | 415 E-steps at 1.8° and 16 microsteps; double it for a 0.9° motor or 32 microsteps | Bondtech FAQ[1] |
| Bondtech LGX Lite (original) | 562 E-steps at 16 microsteps; Klipper gear_ratio example 44:10, 37:17 | Bondtech[2] |
| Micro Swiss NG | No number; a G-code download instead | Micro Swiss[3] |
Bondtech says the original LGX Lite was replaced by the LGX Lite V2, so do not carry its values over to the V2.[2]
Klipper's BMG note
Klipper notes that the BMG is advertised as 3:1 but actually uses 50:17 gearing, which you enter as gear_ratio.[4] That small difference is one reason a copied number is only a start.
The mark-and-extrude method
Klipper's procedure:[4]
- Heat the hotend.
- Mark the filament about 70 mm from the extruder intake and measure to the mark.
- Extrude 50 mm slowly with
G1 E50 F60. - Measure to the mark again. The difference is what actually went in.
- Scale rotation_distance by the ratio of the requested to the actual length, and repeat if the error was over about 2 mm.
Klipper warns that faster rates, or the extrude buttons in a front end, can skew the result, and says not to use this method on the X, Y or Z axes. The ellis3dp.com guide uses a 120 mm mark and extrudes 100 mm at 1 mm/s, and says Bowden setups can be calibrated cold.[5]
In Marlin the idea is the same with E-steps: a new value equals the old value times the requested length divided by the actual length.
Marlin: active is not saved
Marlin's M503 reports the settings currently active in memory, which may not match what is saved in EEPROM. M503 does not save anything; M500 does.[6] After changing E-steps, save it and check that it survives a restart.
Where this sits in the calibration order
Extruder calibration comes first. Klipper tells users to tune rotation_distance and nozzle temperature before tuning pressure advance.[7] The ellis3dp.com guide treats extruder calibration as separate from the extrusion multiplier, which it says to tune per filament brand and type after extruder calibration and pressure advance.[8]
| Step | What it sets | Redo when |
|---|---|---|
| 1. E-steps or rotation distance | Filament the extruder actually feeds | You change the extruder, gears or motor |
| 2. Pressure advance | Pressure lag at speed changes | You change filament, nozzle or extruder |
| 3. Flow ratio | Per-filament fine adjustment | You change filament |
Next
Questions
What E-steps does a Bondtech BMG need?
Bondtech lists 415 E-steps for its BMG with a 1.8° motor at 16 microsteps, and says to double it for a 0.9° motor or for 32 microsteps. Treat that as a starting point and measure.[1]
Why is my measured value different from the maker's?
A published number is a nominal starting point. Klipper notes, for example, that the BMG is advertised as 3:1 but actually uses 50:17 gearing. Measuring what your own extruder feeds is how you find the real value.[4]
Where do I set rotation distance in Klipper?
In the extruder section of your Klipper configuration, as rotation_distance, with gear_ratio if the extruder is geared. Klipper's calibration extrudes 50 mm and scales rotation_distance by what actually went in.[4]
Is E-steps calibration the same as flow rate?
No. The ellis3dp.com guide treats extruder calibration as separate from extrusion multiplier, which is tuned per filament after extruder calibration and pressure advance.[8]
Why does M503 show a different value from what I saved?
Marlin's M503 reports the settings active in memory, which may not match what is saved in EEPROM. M500 saves them.[6]