# How is the E argument calculated for a given G1 command?

I'm working on building a tool to generate G-code (a simpler slicer), and I'm trying to calculate how much filament should be extruded per movement.

Is there a standard calculation for this? Something like:

layer height * flow % * extruder diameter * distance


How does Ultimaker Cura calculate this?

Basically, all movements are (small) straight lines, the volume of a straight line is easily calculated as you already guessed.

To calculate the volume to be extruded you multiply the following parameters:

• the layer height (h)
• flow modifier (e.g. as pertectage) (SF)
• extruder nozzle diameter (d)
• distance of the straight line (l)

With this volume you can calculate how much filament you need to extrude. To get the length (thus the length defined by the E parameter), divide the obtained volume by surface area of your used filament by:

• π * (filament radius)2 or alternatively π /4 * (filament diameter)2

To sum up, the value of E is given by: • Thanks! Just to clarify: extrusionVolume = (layer height * flow modifier * nozzle diameter * straight line distance) E argument = extrusionVolume/π * r2, where r is the radius of the filament? What was the formula you listed after π * r2 (it doesn't look like it's equivalent)? Is it safe to assume that for G2/G3 (arcs), it's the same, but with the perimeter of the arc instead of the distance of the straight line? Jul 5 '18 at 18:39
• @t.gl. Diameter is twice the radius so to get radius squared is similar as diameter squared divided by 4. To calculate arcs (for G2/G3), you need to know the radius of the arc and the section (or angle). Arc circumference is 2 * π * arc radius * percentage of the circle.
– 0scar
Jul 5 '18 at 18:58