Extrusion Multiplier Calibration Calculator
Calculate the correct extrusion multiplier (flow rate) for your 3D printer from measured vs expected filament values.
Extrusion multiplier (called flow rate in some slicers like PrusaSlicer and Cura) is a percentage that scales how much filament your printer pushes during a print. A value of 100% means the printer extrudes exactly what it’s instructed to — but in practice, slight variations in filament diameter, hotend characteristics, and feeder gear grip mean this number rarely lands perfectly at 100%.
The mark-and-extrude calibration method:
- Remove the Bowden tube or directly access the filament path.
- Mark the filament at a known distance from the extruder (e.g., 120 mm up from the entry point).
- Command the printer to extrude 100 mm of filament (via the printer menu or terminal).
- Measure how much filament actually moved. If you asked for 100 mm and got 97 mm, the extruder is under-extruding.
- Plug those numbers into this calculator to get your corrected multiplier.
Formula: New Multiplier = (Expected ÷ Actual) × Current Multiplier
E-steps vs. extrusion multiplier — which to adjust? E-steps (steps per mm) is a firmware-level calibration that defines how many motor steps move exactly 1 mm of filament. This should be set correctly once in firmware and rarely changed. The extrusion multiplier is a per-slicer or per-material override. It compensates for differences in filament brands, diameters, or material behavior without altering firmware. Best practice: calibrate E-steps first using a bare extruder (no hotend resistance), then fine-tune per material with the multiplier.
Acceptable range: A well-calibrated printer should have an extrusion multiplier between 95% and 105%. Outside this range suggests an E-steps problem that should be corrected at the firmware level rather than patched with an extreme multiplier.
Symptoms of incorrect extrusion:
- Under-extrusion (multiplier too low): gaps between lines, weak layer bonding, rough top surfaces, fragile prints.
- Over-extrusion (multiplier too high): blobs, lines merging together, rough and lumpy surfaces, dimensional inaccuracy.
Calibrating extrusion multiplier is one of the most impactful single steps you can take to improve print quality. Even a 3-5% error causes visibly poor surfaces on detailed models.