How is the weight calculated?

The part is split into a solid shell and a hollow interior. Shell volume is approximated as surface area times wall thickness plus top and bottom skins. The interior is the remaining volume, of which only the infill percentage is filled. Total material volume times the material density gives the weight.

Why does 0 percent infill still have weight?

Even hollow prints have solid walls and solid top and bottom surfaces. At 0 percent infill the weight is just the shell. Increasing infill only adds material inside that shell, which is why the jump from 0 to 20 percent is smaller than people expect.

Does doubling infill double the weight?

No. Because the shell is fixed, doubling infill from 20 to 40 percent only doubles the interior contribution, not the whole part. For a thin-walled part with a large interior the change is bigger; for a small, thick-walled part the shell dominates and infill barely matters.

How do I find part volume and surface area?

PrusaSlicer shows volume under Object then Model Info. Cura lists volume in the model information sidebar. Surface area can be read from CAD software or a mesh tool like MeshLab using Compute Geometric Measures. Volume is in cubic centimeters and area in square centimeters.

What infill should I choose for a functional part?

15-20 percent suits decorative and light-duty parts. Functional parts under mechanical load typically use 40-60 percent. Above 60 percent the strength gains diminish while weight and print time keep climbing, so reserve high infill for genuinely load-bearing components.

Infill Density to Weight Calculator

See exactly how much weight (and therefore material and cost) each infill setting adds to a print. The calculator separates the always-solid shell from the variable interior so you can find the lightest setting that still does the job.

How it works

A printed part is two regions: a solid shell and a partly-filled interior.

Shell volume is approximated from the surface area and wall thickness, plus the top and bottom solid skins:

shell volume ≈ surface area × wall thickness + top/bottom skin

Interior volume is whatever is left:

interior = part volume − shell volume

Only the infill fraction of that interior is filled:

infill volume = interior × (infill % ÷ 100)

Total material and weight:

material volume = shell volume + infill volume

weight (g) = material volume (cm³) × density (g/cm³)

PLA density is 1.24 g/cm³, PETG 1.27, ABS 1.04 — picked automatically from the material selector.

Why infill matters less than people expect

Because the shell is fixed, raising infill only changes the interior contribution. For a thick-walled part the shell can dominate, so going from 20% to 40% infill might add only a few grams. For a thin-walled, voluminous part the interior is large and the same change adds much more. The comparison table makes this trade-off explicit per part.

Example

A 50 cm³ part with 90 cm² surface area, 1.2mm walls, 0.8mm top/bottom skins, printed in PLA:

shell volume ≈ 90 × 0.12 + a thin skin term ≈ 11-14 cm³
at 20% infill, interior fill adds roughly (50 − 13) × 0.20 ≈ 7.4 cm³
total material ≈ 20.4 cm³ → weight ≈ 20.4 × 1.24 ≈ 25 g

Bumping to 40% infill adds about another 7 cm³ of material (~9 g). Use the table to pick the lightest infill that meets your strength needs. All computation happens locally in your browser.