Flow Rate (Extrusion Multiplier) Calculator
Calibrate flow (also called extrusion multiplier) for each filament. Do this after your e-steps / rotation distance are correct.
Estimates only. Check numbers against your own slicer, scale and electricity bill. Some links on this page may be affiliate links.
Formulas
Caliper method: new flow = current flow × (line width ÷ average measured wall). OrcaSlicer pass 1: new flow = current flow × (100 + modifier) ÷ 100. Example: line width 0.45 mm, walls averaging 0.48 mm, flow 1.00 → 0.9375 (93.75% in Cura). Orca: 0.98 with best patch +5 → 1.029.
Where to enter it
| Slicer | Setting | Format |
|---|---|---|
| Bambu Studio / OrcaSlicer | Filament → Flow ratio | Ratio (0.9375) |
| PrusaSlicer | Filament → Extrusion multiplier | Ratio |
| Cura | Material → Flow | Percent (93.75%) |
A word of caution
Calipers are only accurate to about ±0.02 mm, which alone shifts the result by ~4%. Ellis' Print Tuning Guide recommends a visual top-surface method over single-wall measurement; OrcaSlicer's built-in flow test is also a visual method. Formula and worked example as described by LayerCalc; Orca procedure from the OrcaSlicer calibration wiki.
Related: print cost · filament length ↔ weight
FAQ
Should I calibrate e-steps or flow first?
E-steps (Marlin) or rotation distance (Klipper) first, because that fixes the extruder hardware. Flow is then tuned per filament.
What is a normal flow ratio for PLA?
Most PLA ends up between about 0.92 and 1.00, but every brand and colour differs, so test each new filament.
Is flow ratio the same as Cura flow percent?
Yes. A ratio of 0.95 equals 95% in Cura.