Filament Weight Calculator

Frequently Asked Questions

How is filament weight calculated from a model?

Weight (g) = model volume (cm³) × material density (g/cm³) × infill fraction (plus shells and supports). PLA ≈ 1.24 g/cm³, PETG ≈ 1.27, ABS ≈ 1.04, TPU ≈ 1.21.

Does infill percentage scale weight linearly?

Roughly, for the infill region only - but perimeters, top/bottom layers, and supports are essentially solid regardless of infill. A 20 cm³ part at 20% infill is closer to 35–45% of its solid weight, not 20%.

How accurate is the estimate vs the slicer?

A volume-based estimate is usually within 5–15% of the slicer's prediction. The slicer simulates real toolpaths (perimeters, gap fill, supports), so use it for final cost; the calculator is great for quick comparisons.

Why does material density matter so much?

Doubling density doubles weight at the same volume. A solid 100 cm³ part is 124 g in PLA but 104 g in ABS - 16% lighter - which can matter for shipping, drone, or RC parts.

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Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How This Calculator Works

The mass of any printed FDM part equals the volume of plastic the printer actually extrudes × the density of the filament. Slicers know this exactly; this calculator gives you the same answer from first principles when you do not yet have a sliced G-code - useful for quoting, comparing materials, or sanity-checking a slicer estimate. You enter either the raw geometric volume (a simple cuboid or cylinder) or the "solid volume" that your slicer reports for an STL, then choose the material and infill percentage. The tool combines a fixed shell allowance (walls, top, and bottom layers print solid regardless of infill) with the fractional infill to get the effective plastic volume, then multiplies by density. The result is grams of plastic on the bed plus, on the next calculator in this set, meters of filament from the spool.

Formula / Method

Solid geometric volume: cuboid = X × Y × Z, cylinder = π × (D ÷ 2)² × H, in mm³, converted to cm³ by ÷1000. Effective fill fraction ≈ shell fraction + (infill % ÷ 100) × (1 − shell fraction). A 20% shell allowance covers typical 3 perimeter walls plus 4 top/bottom solid layers on a midsize part. Effective volume = solid volume × effective fill fraction. Mass (g) = effective volume (cm³) × density (g/cm³). Standard filament densities - PLA 1.24, PETG 1.27, ABS 1.04, TPU 1.21, Nylon 1.14, ASA 1.07, PC 1.20 g/cm³. Carbon-fiber, glass-filled, and metal-filled blends are heavier; check the spool spec.

Worked Example

A 40 × 40 × 20 mm PLA bracket at 20% infill. Solid volume = 40 × 40 × 20 = 32,000 mm³ = 32.0 cm³. Effective fill = 0.20 + 0.20 × 0.80 = 0.36, so effective volume = 32.0 × 0.36 = 11.52 cm³. Mass = 11.52 × 1.24 ≈ 14.3 g - close to what Cura or PrusaSlicer will quote (typically 13–16 g depending on top/bottom count). Switching to PETG at 1.27 g/cm³ lifts the weight by about 2.4% to 14.6 g; ABS at 1.04 drops it to 12.0 g. Doubling infill to 50% pushes effective fill to 0.60 and the weight to 23.8 g of PLA.

Common Mistakes

Treating the bounding box of an STL as the solid volume - a thin-shelled lattice has a fraction of that volume; always use the slicer's reported model volume.

Multiplying STL volume by infill % directly - that ignores the solid shells and underestimates mass for walled parts (a vase mode print is the only case where it is accurate).

Using PLA density (1.24) for PETG or ABS - the spread is small but compounds across a large print.

Forgetting brim, raft, and support material - on a tall thin part, support and brim can add 10–30% to total filament use.

Ignoring filled blends (wood-PLA, CF-Nylon, metal-PLA) - some are 30–80% denser than the base resin.

Tips & FAQ

Why does my slicer say more? Slicers add brim, skirt, prime line, purge tower for multi-material, and support material; this calculator estimates only the model. Add 5–15% for typical extras. Does infill pattern change weight? Slightly - gyroid and cubic at the same percentage extrude essentially the same length; lightning and concentric can be 20–40% lighter at the cost of strength. What density should I use? Match the spool spec sheet; generic PLA varies 1.21–1.27 g/cm³. Does temperature change density? Negligibly for solid parts - thermal expansion is <1% across normal print temperatures. How accurate is this? Within roughly ±10% of slicer output for typical parts; large open shapes (planters, lampshades) need the slicer for honest numbers. Why a 20% shell allowance? A representative midsize functional part with 3 walls and 4 top/bottom layers prints at roughly 18–22% solid regardless of infill; thin parts go higher, large bulky parts go lower. Vase mode? Set infill to 0 and shells to a single perimeter - then the calculator overstates weight; the true volume is just the wall thickness × surface area. This is a planning estimate; let the slicer have the final word before ordering filament for a large job.

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Frequently Asked Questions

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