Work out infill percentage material instantly with clear inputs, formula shown and shareable results.
Walls print solid and only the remaining cavity is filled at the infill density, so material used is walls plus cavity times infill. Because walls are unaffected, raising infill from 20% to 100% on a thin-walled part changes weight far less than it seems it should.
Material volume
volume = wall volume + (model volume - wall volume) x infill density
volume = wall volume + (model volume - wall volume) x infill density. Walls print solid and only the remaining cavity is filled at the infill density, so material used is walls plus cavity times infill.
Because walls are unaffected, raising infill from 20% to 100% on a thin-walled part changes weight far less than it seems it should.
Enter model volume, volume taken by walls and top or bottom, infill density, filament density. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.