How do I measure extrusion width?

Print a single-wall cube or line test. Use digital callipers to measure the wall thickness at several points. Take multiple measurements and average them for a more accurate result. Avoid measuring the first few layers as they may be squished.

What causes over or under extrusion?

Common causes include incorrect e-steps, filament diameter variation, inconsistent tension on the extruder gear, partial nozzle clogs, or incorrect slicer flow settings. Calibrate e-steps first, then fine-tune with flow rate.

How often should I calibrate flow rate?

Calibrate when changing filament type, brand, or colour. Also recalibrate after changing the nozzle or hot end. PLA and PETG often need different flow rates even on the same printer. A change of 1-3% between brands is normal.

3DPrintCalcs

Flow Rate Calibration Calculator

Calculate the correct flow rate multiplier from measured versus expected extrusion width.

Expected Width

Slicer line/extrusion width for this test — PrusaSlicer default is 0.45mm on a 0.4mm nozzle

Measured Width

Single-wall thickness from a vase-mode (1 perimeter) test, measured with callipers

Current Flow Rate

Current flow rate in your slicer

Nozzle SizeNozzle diameter for reference

Number of MeasurementsMore measurements give a more accurate average

How We Calculate This

Formula

Corrected flow = (Expected width / Measured width) x Current flow rate
Over-extrusion = ((Measured - Expected) / Expected) x 100%

If your measured width is wider than expected, you are over-extruding and need to reduce flow. If narrower, increase flow. The goal is to match the slicer's expected line width.

Frequently Asked Questions

Related Calculators

E-Step Calculator

Calculate corrected E-steps from measured vs requested extrusion length for extruder calibration.

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Last updated: March 2026

All calculations are estimates. Always verify settings with test prints before committing to final prints.