Why $/kg is a misleading comparison
Open any filament retailer. PLA is $19.99/kg, PETG is $22.99/kg, ABS is $23.99/kg. The cheapest material is PLA. Done, right?
Not quite. The price you pay per kilogram isn't the price you pay per part. Three variables hide in plain sight:
1. Density determines weight per volume
A 40cm³ part doesn't weigh the same in every material. Density varies:
- PLA: 1.24 g/cm³ → 40cm³ = 49.6g
- PETG: 1.27 g/cm³ → 40cm³ = 50.8g
- ABS: 1.04 g/cm³ → 40cm³ = 41.6g (the lightest common filament)
- PC: 1.20 g/cm³ → 40cm³ = 48.0g
- Nylon: 1.18 g/cm³ → 40cm³ = 47.2g
That's a 22% spread between ABS and PETG for the same printed volume. ABS is the lightest mainstream filament — which means its $/kg gets divided across more parts than the $/kg of PETG does.
2. Failure rate eats real money
Different materials fail at different rates on a typical 3D printer setup:
- PLA: 3–5% (calibration baseline)
- PETG: 5–7%
- ABS / ASA on open frame: 15–30% (drops to 5% with enclosure)
- TPU: 5–9% (depends on retraction tuning)
- Nylon: 8–15% (requires drying)
- Polycarbonate: 8–12%
- Carbon fiber composites (PLA-CF, PA-CF): 4–7% (CF reduces warping)
A failed print costs you the full material plus electricity plus labor — but produces nothing to sell. ABS at 8% failure means 1 in 12 prints is a loss; that's a real cost line that doesn't show up in $/kg.
3. The combined math flips the rankings
For a 40cm³ part comparing PLA Basic (cheap, low failure) vs ASA (premium, moderate failure):
PLA Basic ($19.99/kg, 1.24 g/cm³, 4% fail):
weight = 40 × 1.24 = 49.6g
material = 0.0496 × $19.99 = $0.99
with failure = $0.99 × 1.04 = $1.03
ASA ($27.99/kg, 1.07 g/cm³, 8% fail):
weight = 40 × 1.07 = 42.8g
material = 0.0428 × $27.99 = $1.20
with failure = $1.20 × 1.08 = $1.30
ASA isn't 40% more expensive ($27.99 vs $19.99 = 40% on $/kg). It's 26% more per part because its lower density partly offsets the higher $/kg, while its higher failure rate pulls cost back up. The real difference is more nuanced than the spool price suggests.
When the cheapest pick isn't the right pick
The comparator above always tells you the cheapest material for a given part. But cheapest doesn't always mean best:
- Functional outdoor parts — PLA is cheapest but fails in UV / heat. ASA or PETG is the right answer despite higher cost.
- Customer-facing display pieces — PLA Matte looks better than glossy PLA, even though it's slightly more expensive.
- Production runs — saving $0.05/part matters at volume. Pick the cheapest material that meets requirements.
- Engineering parts — sometimes you need PA-CF or PC even though they're 3–5× more expensive. The premium pays for properties the cheaper materials can't deliver.
What the tool does and doesn't include
Included in the math: material weight, density-adjusted weight per volume, $/kg, failure rate by material, bulk discount.
Not included: electricity, depreciation, labor, platform fees. Those don't vary much between filaments — they vary by print time and printer, which the Pricing Calculator handles per-product.
Use this tool first to pick the material. Use the Pricing Calculator next to set the actual sell price for that material on your printer with your labor rate.
Common questions
Should I always pick the cheapest filament?
Only if all materials meet your requirements. For a phone stand that needs heat resistance, PETG isn't optional just because it costs more. For an indoor figurine where all materials work, the cheapest is usually fine — unless surface quality matters (PLA looks best) or the customer specifically requested a tough material.
How does bulk pricing change the picture?
Buying spools in 5kg or 10kg bundles typically saves 15–25% per kg. Apply that as a bulk discount in section 3 above. The rankings sometimes don't change (cheap stays cheap), but the absolute cost gap between options shrinks — making the "premium" filaments more justifiable per part.
What about exotic materials (TPU, flexible, conductive)?
TPU is included in the comparator. Conductive, glow-in-dark, dissolvable, and other specialty filaments aren't — they're priced per-application and the database focuses on filaments you'd realistically choose between for the same part. For specialty work, calculate cost manually using the $/kg × weight method.
Frequently asked questions
Why does this matter when I can just compare $/kg?
Three reasons. (1) Density varies — PETG is 2.4% denser than PLA, so a 50cm³ part weighs more in PETG than in PLA, eating into the per-part cost. (2) Failure rate varies — ABS at 8% failure costs more per successful print than PLA at 4%, even at the same $/kg. (3) Material type changes the math — Nylon, TPU, and carbon-fiber composites all have different real per-part costs that $/kg comparisons miss. This tool factors all three.
Why are PLA and PLA+ priced almost the same per part?
Because they have essentially the same density (~1.24 g/cm³) and similar failure rates. The $/kg difference (~10-15%) is the only real cost variable. PLA+ is usually worth the small premium for any functional product because the impact resistance improvement is significant. For decorative or display pieces, plain PLA is fine.
How accurate are the failure rate defaults?
They're calibrated to a tuned printer in standard conditions: PLA 4%, PETG 5%, ABS 8% (much higher on open-frame printers — bump to 15-20% if you don't have an enclosure), Nylon 10%, TPU 7%. Use the failure-rate multiplier (in section 3) to scale up or down for your shop's actual numbers. A multiplier of 1.5× covers most under-tuned printers; 0.5× covers print farms with calibrated workflows.
Does this work for resin printing?
No — resin has fundamentally different cost structure (FEP wear, LCD lifetime, IPA cycles, wash & cure power). Use the dedicated Resin Cost Calculator for resin per-part economics. This tool is FDM filament only.
I bought my spool on sale — can I model that?
Yes. Open the "failure rate per material" section and apply a bulk discount percentage. 20% discount means each filament's $/kg is multiplied by 0.80 for the calculation. Useful for modeling bulk-buy pricing or sale prices.
How is this different from the Pricing Calculator?
The Pricing Calculator gives you the full cost (material + electricity + depreciation + labor + failure + platform fees) for ONE filament. This tool compares ONLY material cost across many filaments at once. Use this tool first to pick the right material, then use the Pricing Calculator to set your sell price with that material chosen.
What about carbon fiber filaments?
They're included — PLA-CF and PA-CF appear in the comparison. CF composites are typically 2–3× the cost of base material per kg but have similar density. Worth the premium when CF's reduced shrinkage and higher stiffness matter (functional prints, jigs, fixtures). Not worth it for decorative work.
Where do the density numbers come from?
Manufacturer-published density values from each filament's spec sheet. Standard values: PLA 1.24, PETG 1.27, ABS 1.04, Nylon 1.18, TPU 1.20, PC 1.20 g/cm³. Differences within 0.05 g/cm³ exist between brands but are negligible for cost comparison purposes.