Amount of material extrusion:

[anshuman 0]

What all parameters does Cura take into consideration when it decides the amount of material it should extrude through the nozzle?

I am trying to write a G-code manually but the print does not come out good as amount of material specified is maybe not right.

[gr5 1,256]

First of all I assume you are in reprap mode as the UM2 and UM3 support a weird mode called ultigcode but can also do reprap mode. Every other printer in the world does normal gcodes basically.

The extrusion is in mm length of filament. So it matters the diameter of the filament.

For example lets say you print a "line" of filament 100mm long. Let's say the nozzle is .4mm wide and the layer height is .1mm. The volume of filament is 100*.1*.4 or 4 cubic mm.

If you have 1.75mm diameter filament the area of that filament is PI * (1.75/2) ^2 or 2.4 mm^2 area. 4 / 2.4 gives you 1.666mm of travel for E axis.

So if E had been at position zero and x,y was at 0,0 then you could do something like

G0 X100 Y0 E1.666

You can also reset the extruder (or any axis) with G92 command so for example even if extruder is 2 meters into a print job you can do:

G92 E0

G0 E1.666

and it would extrude the amount of filament for a 100mm long line at .1mm layer height and .4mm nozzle width.

That's how Cura does it.