OrcaSlicer Calibration Calculator: PA, Flow

Short answer: The Orca Slicer Assistant is three small formulas for turning OrcaSlicer's built-in calibration test prints into the setting values you enter in your filament profile: pressure advance, flow ratio and retraction length. You print the test, measure or read off the best result, and do one multiplication or addition. The steps follow the OrcaSlicer calibration guide.

The original page had an interactive calculator, but the editor stripped out its input boxes and it stopped working. The formulas below do the same job and work in any calculator.

Pressure advance

Pressure advance is a firmware setting (pressure advance in Klipper and Bambu, linear advance in Marlin) that compensates for the delay between the extruder pushing filament and plastic leaving the nozzle. It sharpens corners and evens out lines when the speed changes. OrcaSlicer's tower test raises the value by a fixed step for every millimetre of height.

Formula: Pressure advance = PA step (A) × measured height of the best section in mm (B)

Example: a direct-drive (DDE) tower with a 0.002 step that looks best at 20 mm gives 0.002 × 20 = 0.040. Bowden setups use the same formula, but expect a much larger value because of the long tube.

Flow rate

Flow rate (flow ratio) is the multiplier OrcaSlicer applies to the amount of plastic it extrudes, which corrects small differences in filament diameter and extruder calibration. In the flow test you print a set of blocks labelled with modifiers (for example −5 to +5) and choose the one with the smoothest top surface.

Formula: New flow ratio = current flow ratio × (100 + modifier) / 100

Example: current flow ratio 0.98 and the best block is +3: 0.98 × 103 / 100 = 1.0094.

Retraction

Retraction length is how far the extruder pulls filament back before a travel move to stop stringing. OrcaSlicer's retraction tower starts at a set length and adds a fixed amount per millimetre of height.

Formula: Retraction length = start length + (measured height in mm × factor)

Example: start 0 mm, factor 0.1 mm per mm and strings disappear at 8 mm: 0 + 8 × 0.1 = 0.8 mm.

FAQ

In what order should I calibrate in OrcaSlicer?

OrcaSlicer's calibration guide recommends this order: temperature, max volumetric speed, pressure advance, flow ratio, then retraction. Pressure advance comes before flow ratio because it is the value most often wrong, and retraction comes last because both of the others change the pressure in the nozzle.

Do I need to recalibrate for every filament?

Recalibrate when you change filament brand or type: flow ratio and pressure advance can differ between brands, even for the same material.

Where do I enter the results?

Enter the results in the filament profile: flow ratio and pressure advance are under the filament settings, and retraction can be overridden per filament or set in the printer profile.

Original calculator by @StonedModder (GitHub), modified by MakerViking.