Line Width Calculator

Line width (extrusion width) is how wide each deposited bead of plastic is. Slicers often default to 100–120% of nozzle diameter — a 0.4 mm nozzle might print 0.42–0.48 mm lines. Wider lines increase strength and speed; narrower lines improve detail.

Nozzle size sets the physical orifice; line width is a slicer setting that can slightly exceed nozzle diameter through controlled squish. Going too wide causes poor quality; too narrow causes under-extrusion.

Example: 0.4 mm nozzle × 1.2 multiplier = 0.48 mm line width. A 0.6 mm nozzle at 1.0× = 0.6 mm lines.

A printed line is not round, and that is the whole point. Plastic leaves a circular nozzle and is then flattened against the previous layer, so the bead ends up roughly rectangular with rounded ends — wider than the orifice and as tall as the layer height. Deliberate squish is what bonds neighbouring lines into a solid wall.

Practical limits sit around 60% to 200% of nozzle diameter, with 100% to 120% as the everyday range. Too narrow and the extruder cannot push a consistent thread, producing gaps and weak walls; too wide and the bead loses definition, corners bulge, and the excess plastic has nowhere to go but up.

Layer height constrains line width in both directions. A useful rule is to keep layer height at or below about 75% of nozzle diameter and line width at or above layer height; a 0.4 mm nozzle therefore works well up to roughly 0.3 mm layers, and pairing a tall layer with a narrow line is what causes poor interlayer bonding.

Wall count interacts with line width to decide whether a wall fits at all. A 1.6 mm rib takes exactly four 0.4 mm lines but only three at 0.53 mm, leaving a gap the slicer must fill or ignore. Choosing a line width that divides evenly into your critical wall thicknesses removes those artefacts.

Different line widths apply to different features, so enter the one you are tuning. First layer is usually set wider — often 120% to 140% — for bed adhesion; outer walls are frequently narrowed slightly for detail; infill can be widened well past the nozzle diameter to save time, since it is never seen.

Line width feeds layer time estimates — once you settle on nozzle and multiplier settings, run the layer time calculator with your speed caps to see whether small features need minimum-layer-time overrides.

First-layer line width is often set wider than outer walls for bed adhesion — enter the setting you are tuning (initial layer vs perimeter) to match what you see in the slicer preview.

Variable layer height changes extrusion volume per layer — line width math assumes consistent layer height with your nozzle setup.