1
Print
A single-wall hollow cube at your target line width. 20mm works. One perimeter, zero top, zero infill.
2
Measure
Use calipers on all four walls, halfway up, not on seams. Record each reading.
3
Apply
Copy the new flow value into your slicer (Flow / Extrusion Multiplier) and reprint to confirm.
Extrusion multiplier
From measured wall thickness
mm
Match the line width you used when slicing the cube.
Measure each face mid-height. Blank slots are ignored.
%
Cura & PrusaSlicer default is 100. Bambu Studio calls it Flow ratio (1.0 = 100).
New flow
100.0%
Enter a wall reading to calibrate.
new flow = current flow × (target / measured avg)
A quick sanity check: most PLA lands between 92% and 104% flow. Outside that range, suspect a caliper reading, the wrong target line width, or a clogged nozzle before changing flow.
E-steps per mm
Firmware-level extruder calibration
steps/mm
Typical: Ender 3 stock 93, BMG clone 415, Bondtech LGX 562, Bambu X1C 690.5.
mm
Standard test: mark 120mm from extruder, extrude 100mm at 2mm/s, hot.
mm
If 18.5mm remains from your 120mm mark, you extruded 101.5mm.
New E-steps
415.00steps/mm
Enter actual extruded to calibrate.
new E = current E × (requested / actual)
Write the new value to firmware with
M92 E<value> then M500 to save. Klipper: update rotation_distance instead.
Do flow after E-steps
Bad E-steps skew every flow reading. Calibrate the extruder first, then flow, then temperature, then retraction. One variable at a time.
Per-material, not per-printer
Flow changes with filament brand, colour, moisture, and even spool-to-spool. E-steps are hardware. Save flow profiles per material, save E-steps once.