OrcaSlicer Flow Rate Calibration

The Flow Rate Calculator turns your OrcaSlicer flow test result into a corrected flow ratio. There’s also a YOLO method calculator for the single-pass approach and a traditional calibration calculator for the measure-the-wall method.

Free, runs in your browser, no registration.

What flow rate actually controls

Flow ratio (OrcaSlicer’s term; extrusion multiplier elsewhere) scales how much filament is extruded relative to what the slicer calculated. Default is 1.0 for most profiles.

It corrects for the gap between theory and reality — filament diameter variation, how much the polymer swells leaving the nozzle, and material differences the slicer can’t know about.

Symptoms of flow too low: gaps between top-layer lines, visible perimeter separation, weak parts. Symptoms of flow too high: rough or ridged top surfaces, blobbing, over-full corners, dimensions creeping oversized.

Do rotation distance first

This is the mistake that costs people entire evenings.

Flow ratio and rotation_distance both change how much plastic comes out. If your rotation distance is wrong, you can compensate with flow ratio and get a decent-looking print — but the error now lives in the wrong place, and it will break the moment you change filament, since flow ratio is per-filament and rotation distance is per-printer.

Calibrate rotation distance first. Always. Then flow.

The two methods

YOLO method (recommended)

The current OrcaSlicer approach, and faster than the older two-pass version.

1. Calibration → Flow Rate → Pass 1
2. Print it. Look at the top surface of each numbered patch.
3. Pick the patch with the smoothest top surface — not the shiniest, not the one with visible lines. You are looking for the one where lines have just merged without over-filling.
4. Feed the number into the YOLO calculator. The new flow ratio is current_ratio × (1 + modifier/100).
5. Apply it in Filament Settings → Flow ratio.

Traditional / measured-wall method

Slower, but it removes the subjective judgment.

1. Print a single-wall calibration cube — one perimeter, no top or bottom layers, no infill.
2. Measure the wall thickness with calipers at several points on each face. Average them.
3. Enter your target line width and the measured average into the traditional calculator.
4. new_flow = old_flow × (target_width / measured_width)

The measured method is better when you’re chasing dimensional accuracy. The visual method is better when you’re chasing surface finish. They rarely disagree by much.

Reading the test print honestly

The most common failure here is picking the shiniest square. Gloss usually means slightly over-extruded — the surface is being ironed flat by excess material.

What you want is the square where the extrusion lines have just fused into a continuous surface with no visible valleys and no ridging. If you’re between two squares, take the lower one. Slight under-extrusion is more forgiving than slight over.

Look at it in raking light, not straight on.

Flow is per-filament

Set flow ratio in Filament Settings, not Printer Settings. Different brands of the same material genuinely differ — a 2% swing between two PLA spools is normal, and colorant loading changes it too.

If you use a handful of filaments regularly, calibrate each once and save it in the filament profile. That’s five minutes per spool type, once, forever.

Common mistakes

• Calibrating flow before rotation distance. See above. This is the big one.
• Picking the glossiest square. Gloss is over-extrusion.
• Setting it per printer. It belongs to the filament.
• Recalibrating for every new spool of the same brand and colour. Diminishing returns; batch variation is usually under 1%.
• Chasing flow to fix a problem that’s actually temperature or moisture. Wet filament looks like inconsistent flow and no amount of ratio tuning fixes it. Dry the spool first.

Where this sits in tuning

1. Rotation distance
2. Flow rate ← you are here
3. Max volumetric speed
4. Pressure advance
5. Extrusion rate smoothing

Related tools

• Shrinkage Calculator — dimensional accuracy after flow is right
• Line Widths Calculator
• Temperature Tower Calculator
• All Calculators

Verified profiles

Calibrated flow ratios for the filaments I actually print are included in the Minimal 3DP OrcaSlicer profiles, along with the test prints they came from. My raw configs remain free in the klipper repository.