3D Printing Calculators

3D design & tolerances

Wall Thickness vs Line Width

A 1.7 mm wall with 0.42 mm lines is not four perimeters — it is three lines and a starved gap. Round to n × width, or change width so n × width equals the CAD thickness.

Inputs

Units
mm
mm

Often 100–120% of nozzle diameter.

Two perimeters is the usual watertight / strength floor.

Results

Line count
4
Wall at that count
1.680mm
Error vs CAD
0.080mm
Line width for an exact hit
0.400mm

Recommended gear

Calculation method

Divide the CAD wall by extrusion width and round to a whole number of lines, never below the minimum you set (usually 2). The actual wall is n × width; the error is how far that missed CAD. Suggested line width is the target divided by n so you can keep the CAD thickness and change the slicer instead. Widths are millimetres; the unit toggle shows inches.

Exact formula

n = max(min_lines, round(target / line_width)). actual = n × width. error = |actual − target|. suggested_width = target / n. Limits: Integer lines only. Arachne, vase mode and variable-width features can ignore this. Confirm the slicer preview.

Nozzle first, width second

A 0.4 mm nozzle wants ~0.40–0.48 mm lines. Do not set 0.80 mm width on a 0.4 mm hole just to hit a CAD wall — change the CAD or the nozzle.

Frequently asked questions

PrusaSlicer Arachne already varies width?

It can fill leftovers. Classic perimeter mode still loves integer walls. Use whichever your profile actually runs.

Strength vs 1.6 mm on 0.4 mm?

Four 0.42 mm lines is 1.68 mm — close. Three lines is 1.26 mm and weaker.

Include the outer line in the count?

Yes. n is total traces through the wall, not extra inner walls only.

Does flow % change this?

Yes. 95% flow prints a thinner wall than this geometry. Recheck with a caliper.

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