How to calibrate flow rate
- Calibrate e-steps first if you have not already.
- Model a hollow 20 mm cube, or use a calibration cube, and slice it with 0% infill, no top layers, and 2 walls.
- Note the line width your slicer uses for outer walls (often 0.42–0.45 mm for a 0.4 mm nozzle).
- Print it, let it cool, and measure each side’s wall thickness with calipers. Average the readings.
- Enter the values above and set the new flow (or extrusion multiplier) in the filament profile.
Expected wall = walls × line width
New flow = current flow × expected wall ÷ measured wall
Worked example
- Expected wall: 2 × 0.45
- 0.90 mm
- Measured wall
- 0.94 mm
- New flow: 100 × 0.90 ÷ 0.94
- 95.7%
- Extrusion multiplier
- 0.957
Frequently asked questions
Flow rate or extrusion multiplier: which is it?
The same setting with different names. Some slicers use a percentage (95.7%), others a ratio (0.957). The calculator shows both.
How do I know flow is wrong?
Too high: rough top surfaces, blobs and parts that are slightly oversized. Too low: gaps between lines, weak layers and holes in the top surface.
Should flow be calibrated for each filament?
Yes, ideally for each brand and material. Diameter and melt behaviour vary between spools, so save the value in each filament profile.
Last reviewed October 2026. See how we calculate.