Infill Calculator
Estimate extruded plastic volume and filament weight from model volume, infill percentage, and shell share. Free and instant.
A 100 cm³ model at 20% infill uses about 32 cm³ of plastic — 39.7 g of 1.24.
How it works
Estimate how much plastic a print actually uses. A printed part is solid walls, top and bottom layers, plus sparse infill inside. Enter the model volume, your infill percentage, and roughly what share of the volume the solid shell takes (15% is typical for medium parts), and we estimate extruded volume and weight.
- Plastic volume = V × shell% + V × (1 − shell%) × infill%
- Weight = plastic volume × material density
- Small parts have a larger shell share (20–30%); big boxy parts less (~10%)
Enter model volume, infill percentage, shell share and material for extruded plastic volume and filament weight. Getting the shell share roughly right matters more than getting infill exactly right, since it is the shell that dominates on typical parts. The output feeds directly into the print cost calculator and print time estimator, which both work from extruded volume rather than model volume. One caveat: infill pattern affects the real figure too — gyroid and cubic use slightly more material than a simple grid at the same nominal percentage, so treat this as a good estimate rather than the slicer's exact number.
Frequently asked questions
How much plastic does a print actually use?
Far less than the model volume. A 100 cm³ model at 20 percent infill with a typical 15 percent solid shell uses about 32 cm³ of plastic — roughly 40 g in PLA. The shell is solid regardless of infill, which is why the walls and top and bottom layers account for most of the plastic in small parts.
What shell share should I use?
About 15 percent for a medium part, 20 to 30 percent for small ones, and around 10 percent for large boxy shapes. The reason is surface-area-to-volume ratio: a small part is nearly all surface, so its solid perimeters and top and bottom layers dominate, while a big hollow box is mostly interior.
Does more infill make a part stronger?
Up to a point, and with diminishing returns. Going from 20 to 40 percent adds meaningful strength; going from 60 to 100 percent adds weight and time for little gain, because at high infill the failure mode shifts to layer adhesion rather than internal density. Extra perimeters are usually a better investment than extra infill for load-bearing parts.
Examples & notes
- Typical 20% infill part
- Large light PETG part
- Strong small ABS part
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