Infill Cost Calculator

Frequently Asked Questions

How is per-part filament cost calculated?

Cost ($) = part weight (g) × spool price ($) ÷ 1000. A 60 g part on a $25/kg spool is 60 × 25 ÷ 1000 = $1.50 in plastic, before electricity and wear.

How much does infill % change cost?

For a 100 g solid part, 20% infill might land near 45 g, 50% near 65 g, 100% solid is 100 g. Going from 20% → 50% on a $25/kg spool adds only ≈$0.50 - usually worth it for structural parts.

Does infill pattern matter for cost?

Slightly. Gyroid and cubic use similar material to grid for a given %, but Lightning infill can cut material 30–60% versus standard patterns for non-structural display prints, dropping cost proportionally.

What about waste filament?

Add 3–8% for purge, prime lines, brims, and failed first layers; multi-color prints with a purge tower can waste 30–80%. The calculator lets you set a waste factor so multi-material jobs aren't under-quoted.

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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

Infill is the single biggest lever for material cost on FDM parts. Shells (perimeter walls and the top/bottom solid layers) print solid regardless of infill, but the internal volume between them is filled at whatever percentage you choose. Doubling infill from 20% to 40% does not double cost - it raises only the interior portion. This calculator computes filament weight and dollar cost at four common infill levels (10, 20, 50, 100%) for the same model, so you can see what a denser fill actually costs and decide whether the strength gain is worth it. Inputs: the slicer's reported solid model volume in cm³, the price per kg of your filament, and a shell allowance that captures how much of the model prints solid at any infill setting.

Formula / Method

Effective fill fraction = shell fraction + (infill % ÷ 100) × (1 − shell fraction). Plastic mass (g) = model volume (cm³) × effective fill fraction × density (g/cm³). Cost ($) = mass (kg) × price ($/kg). Standard densities: PLA 1.24, PETG 1.27, ABS 1.04, TPU 1.21, Nylon 1.14, ASA 1.07, PC 1.20 g/cm³. A typical 3-wall + 4 top/bottom-layer part has a shell allowance of about 20%; thin or hollow parts go higher, large blocky parts lower.

Worked Example

A 32 cm³ PLA bracket at $22/kg, 20% shell allowance. At 10% infill: effective fill = 0.20 + 0.10×0.80 = 0.28, mass = 32 × 0.28 × 1.24 ≈ 11.1 g, cost ≈ $0.244. At 20%: 0.36 → 14.3 g → $0.314. At 50%: 0.60 → 23.8 g → $0.524. At 100% (solid): 1.00 → 39.7 g → $0.873. Doubling from 20% to 50% adds only $0.21; going to fully solid roughly triples cost vs 20%. For a typical functional part where 20% is plenty strong, paying for 100% infill is throwing money on the bed.

Common Mistakes

Assuming cost scales linearly with infill percentage - it does not; shells dominate at low infill.

Using bounding-box volume instead of true model volume from the slicer - can overstate cost by 5× on hollow models.

Forgetting price differences between materials - budget PLA at $15–20/kg vs prosumer Polymaker at $30+, premium engineering filaments $50–80/kg.

Ignoring waste, brim, and purge tower - a multi-color print can spend 30–50% of total filament on purge.

Choosing 100% infill "to be safe" - rarely improves real-world strength because the shell already governs.

Tips & FAQ

What infill % do I actually need? For decorative parts, 10–15%. For most functional parts, 20–25% with 3 walls. For load-bearing brackets, 30–40% with 4–5 walls. Going above 50% rarely improves strength and mostly adds weight and print time. Does pattern matter for cost? Roughly the same grams per percentage point across grid, cubic, gyroid; lightning and concentric are cheaper at the cost of strength. How do I cut cost more? Walls beat infill for strength - 4 walls at 15% often outperforms 2 walls at 40%, and uses less filament. Why is my actual usage higher? Slicers add brim (1–3 g), purge, and (on multi-material) a purge tower that can dwarf the part. Engineering filament economics? A $60/kg Nylon at 20% infill on a 30 cm³ part costs about $0.85 - cheap compared to a CNC alternative; cost rarely justifies switching to a weaker material. Does layer height affect cost? Not the model mass, but it affects print time. Estimate only - the slicer has the final word.

Frequently Asked Questions

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