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Flow Rate Calculator (Extrusion Multiplier)

Print a single-wall cube in vase mode, measure the wall in a few places with calipers, and enter the readings. New flow = current flow × expected wall width ÷ measured average. Download the test cube here, then copy the new value into your slicer.

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Demo with a sample file, recorded in this tool.

How to calibrate flow rate

  1. 1

    Download the cube

    Pick a size and download the test cube STL. It is a plain solid cube: the slicer turns it into a single wall in vase mode.

  2. 2

    Slice in vase mode

    Turn on spiral vase (Spiralize outer contour in Cura), set the line width you want to test (for example 0.45 mm), 0 top layers. Print it with your usual filament and speed.

  3. 3

    Measure the wall

    Measure the wall on each side, a little above the bottom, with calipers. Enter 2 to 8 readings; the calculator averages them.

  4. 4

    Update your slicer

    Enter your current flow % or extrusion multiplier and copy the new one into the filament settings. Print a second cube to confirm.

Where the setting is in your slicer

Every slicer has the same setting under a different name. Some store it as a percentage, some as a ratio around 1.0.

CuraFlow (Material section), in %. 100% = no change. There are also per-feature flows, such as wall flow; change the main one.
PrusaSlicer, SuperSlicerExtrusion multiplier (Filament settings > Filament), as a ratio such as 0.95.
OrcaSlicer, Bambu StudioFlow ratio (Filament settings), as a ratio such as 0.98. OrcaSlicer also has its own flow-rate test prints in the Calibration menu.
Simplify3DExtrusion multiplier (Extruder tab), as a ratio.
Klipper, Marlin at print timeM221 S<percent> changes flow for the current print only. Use it to try a value, then set it in the slicer.

Printer tuned? Make a printable model with AI

Turn a photo or a sentence into a 3D model with an STL download, ready to slice. The AI generators use credits; this calibration tool does not.

Photo to STL with AI →Text to 3D model

More free 3D printing tools

E-steps calculatorTemperature tower generatorRetraction test generatorTolerance test generatorWall thickness checker

Flow rate FAQ

New flow = current flow × expected wall width ÷ measured wall width. If you print a single wall at 0.45 mm and it measures 0.48 mm, new flow = 100% × 0.45 ÷ 0.48 = 93.75%. Use the average of several readings, not one.
The extrusion (line) width set in your slicer for the outer wall, for example 0.45 mm with a 0.4 mm nozzle. In vase mode the cube has exactly one wall, so the measured thickness should match that width.
They are the same thing in different units. Cura shows flow in % (100%), PrusaSlicer, OrcaSlicer and Bambu Studio use a ratio (1.00). The calculator accepts either and gives you both.
Yes. E-steps makes the extruder push the length it is asked for and is set once per printer. Flow then corrects the small difference of each filament. If e-steps are off, every filament will need a large flow change.
Use digital calipers and measure each side at a similar height, away from the seam and corners. A 0.01 mm error on a 0.45 mm wall moves the result by about 2%, so averaging four or more readings matters.
Check the line width you entered matches the slicer, that the cube really printed with one wall (vase mode), and that e-steps are calibrated. A change of more than about 10% usually means one of those is off rather than the filament.
It can. Hotter or slower printing lets more plastic through, very fast printing can starve the nozzle. Calibrate flow at the temperature and speed you normally print with, after the temperature tower.

The result is plain arithmetic from the readings you enter. Slicers round flow differently; print a second cube to confirm the new value.