Calibrate flow ratio / extrusion multiplier

This is where the great majority of "I am over-extruding" and "my dimensions are off" problems actually resolve. It is only valid once e-steps, filament diameter, and temperature are settled.

Phase 3 — Flowabout 45 minper filament

How to do it

  1. Find it in your slicer first. OrcaSlicer and FlashStudio call this FLOW RATIO; PrusaSlicer and SuperSlicer call it EXTRUSION MULTIPLIER; Cura calls it FLOW. Same number, three names.
  2. Check which scale yours uses. Flow ratio is a decimal where 1.0 means 100%; extrusion multiplier and Cura flow are percentages. 0.98 and 98% are the same setting.
  3. Print the single-wall flow cube — one perimeter, zero infill, zero top layers.
  4. Measure each wall with calipers at three heights, avoiding the seam.
  5. Average the readings.
  6. new_flow = old_flow × (target_width / measured_width)
  7. Re-print and confirm.

How to read the result

Measured wall thickness matches the commanded line width. Thicker means reduce flow; thinner means increase it.

Your slicer may do this for you

OrcaSlicer and SuperSlicer have a flow rate test under Calibration; Bambu Studio calls its version flow dynamics.

Redoing this invalidates

Calibration is a chain. Change this and the results below were measured against the old value:

Open First Layer →
The app walks this in order, generates the test model for your nozzle and filament, and records what you measure so nothing has to be repeated. Free, no account, works offline.