3D Print Part Weight & Infill Calculator

How it works

plastic volume = min(V, surface area × wall thickness) + (V − shell) × infill% · weight = volume × density · length = volume ÷ (π × (filament diameter ÷ 2)²)

A slicer prints a part as a skin of solid walls and top/bottom layers wrapped around a sparse lattice, so its weight is the shell plus a fraction of what is left inside. Multiplying surface area by wall thickness gives a good shell estimate for anything that is not paper-thin, and the remaining interior volume scales directly with the infill percentage. Because the shell is fixed, the savings from lowering infill are much smaller than the percentage suggests — dropping from 20% to 10% on a typical part saves only a few grams — while adding walls costs little and improves strength dramatically. Density converts volume to grams and, with the filament cross-section, to metres on the spool.

Worked example

A 50 cm³ model with 150 cm² of surface, 1.2 mm walls and 20% infill: the shell is 150 × 0.12 = 18 cm³, the interior 32 cm³ contributes 6.4 cm³, so 24.4 cm³ of PLA weighs 30.3 g, costs about $0.67 at $22/kg and uses 10.1 m of 1.75 mm filament — 49% of the 62 g a solid print would need.

Frequently asked questions