Extrusion Multiplier Calculator

What is the extrusion multiplier?

The extrusion multiplier (sometimes called flow rate in slicer settings) is a correction factor applied to every extrusion move your printer makes. If your printer consistently pushes out less filament than commanded, prints come out weak, with visible gaps between lines. Push out too much, and you get blobbing, dimensional inaccuracy, and clogged nozzles over time.

How to test it

The classic test: mark the filament 120mm above the extruder entry point, then command the printer (via your control software or slicer's manual extrusion) to extrude exactly 100mm. Measure how far the mark actually moved. If it moved only 95mm, your printer is under-extruding.

Worked example

Say you commanded 100mm of extrusion but only 95mm actually fed through:

Multiplier = Expected / Actual = 100 / 95 = 1.0526

Enter 1.0526 as your slicer's flow rate or extrusion multiplier (or 105.26% depending on how your slicer expresses it) to correct the under-extrusion.

Frequently asked questions

Do I need to redo this test for every filament? Ideally yes, especially when switching between materials with different diameters or hardness, since each can feed slightly differently through the extruder gear.

Is this the same as E-steps calibration? No. The extrusion multiplier is a slicer-side software correction, while E-steps calibration corrects the firmware value that controls how far the extruder motor thinks it moves per step. Either approach fixes the same symptom, but E-steps calibration is more permanent since it lives in the printer's firmware rather than each slicer profile.