Flow Rate / Extrusion Multiplier Calculator

Print a single-wall or two-wall calibration cube, measure the wall thickness with calipers, and enter it below. We'll calculate your corrected flow rate percentage.

Inputs

Your slicer's current flow / extrusion multiplier setting

Usually 0.4-0.5mm for a 0.4mm nozzle

Measure with calipers at mid-height

Target thickness: 0.900mm (2 walls × 0.45mm)

How to calibrate flow rate

  1. 1Set your slicer to print a hollow box or single-wall cube with known line width (e.g. 0.45mm) and 1-2 walls, no top/bottom layers.
  2. 2Print the calibration object and let it cool completely.
  3. 3Measure the wall thickness with digital calipers at 3-4 points at mid-height and average the readings.
  4. 4Enter the values above. The calculator gives you the corrected flow %.
  5. 5Update your slicer profile and print again to verify. Repeat until within +/-0.05mm.

FAQ

What is extrusion multiplier / flow rate?

It's a slicer setting (usually 0.9-1.1 or 90-110%) that scales how much filament the printer extrudes. 100% means the printer extrudes exactly the theoretical volume. Tuning it corrects for filament diameter variations and hotend characteristics.

Should I calibrate flow rate before or after E-steps?

E-steps first, always. E-steps calibrate how many motor steps equal 1mm of filament movement. Flow rate then fine-tunes actual deposition at the nozzle. Getting E-steps wrong will make flow rate calibration meaningless.

Does Bambu Lab need flow rate calibration?

Bambu printers run automatic flow calibration before each print. However, when using third-party filament with custom profiles, manual flow tuning can still improve results - especially for PETG and flexible materials.

What's a normal flow rate value?

Most PLA prints well at 95-105%. PETG often needs 92-98% as it tends to over-extrude. ABS typically 96-100%. If you're outside 90-110%, check your filament diameter and E-steps first.

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