Flow Rate Calibration Calculator
Fine-tune how much plastic lands on the part. Print a test wall, measure it, and this gives the corrected flow percentage and extrusion multiplier to enter in your slicer for crisp, dimensionally accurate prints.
The flow or extrusion multiplier used when you printed the test — 100% (or 1.0×) if untouched.
Target is what the wall should be. Measure the printed wall with calipers at several spots and average them.
Work out the target from your slicer
A single-wall test at 0.40 mm line width has a 0.40 mm target. Setting these fills the target above; type in Target directly to override.
Formula & how it works
Corrected flow = current flow × target wall ÷ measured wall. A wall that printed too thick means you were over-extruding, so flow drops; too thin means flow rises.
The extrusion multiplier is the same value as a decimal: flow ÷ 100.
Worked example
You print a single-wall cube meant to be 0.40 mm at 100% flow, and calipers read 0.44 mm — over-extruded. Corrected flow is 100 × 0.40 ÷ 0.44 = 90.9%, an extrusion multiplier of 0.909. If instead it measured 0.38 mm, flow would rise to about 105% to build the wall back up.
Measuring flow the right way
Use a clean single-wall test
The most reliable flow test is a hollow object printed with a single perimeter and no top, bottom, or infill, so the wall is exactly one line wide. That way the measured thickness maps directly to line width, and there is no infill pushing the walls outward to confuse the reading.
Average several measurements
Printed walls are never perfectly uniform, so measure at several heights and around the sides, then average. A single reading can land on a blob or a thin spot and send your flow the wrong way. Squeeze the calipers gently — pressing hard compresses the plastic and reads low.
Order matters: E-steps, then flow
Flow calibration assumes the extruder already feeds the right amount of filament. If E-steps are off, you are chasing two errors at once and the flow number will drift. Get the extruder feeding accurately first, then use this to trim how much plastic actually lands on the wall.