Filament Cost Calculator

How this works

3D print filament is sold by the kilogram, but prints use grams. The math: convert grams to kg, multiply by price per kg, then add a waste factor. Waste covers priming, skirts, brims, and small-scale failures, not full print failures, which need to be amortized separately.

This calculator does not convert between currencies or unit systems. If your spool price is in Euros, select EUR. If you bought a 750 g spool for $25, your price per kg is $33.33. A quick spool pricing reference lives in the FAQ below.

The formula in detail

Strip everything else away and the math is one line:

cost = (grams / 1000) × price_per_kg × (1 + waste_factor)

Worked example. Your slicer says a print uses 87 grams. You bought a 1 kg spool of Polymaker PolyTerra PLA for $22. You typically see 5% waste. Math: (87 / 1000) × 22 × 1.05 = $2.01. That print costs you two bucks in filament alone.

The waste factor is where most online calculators get sloppy. Some ignore it entirely and quote you the raw filament cost. Others stack a 20% buffer to "be safe," which inflates the number for no good reason on a clean printer. The defaults here come from real community data: 5% PLA, 7% PETG, 8% TPU, 10% ABS. Adjust if your specific printer runs hotter or cooler than typical.

What "waste" actually covers

The waste factor in this calculator only counts waste on completed prints. That includes:

• Nozzle priming line at the start of every print (1 to 3 grams)
• Skirt or brim, if you slice with one (2 to 8 grams)
• Stringing and oozing during travel moves (varies by material; PETG and TPU are the worst)
• Small surface defects you reprint, like a single failed corner on a multi-part plate

What it does NOT cover: full print failures (the print delaminated at hour 6 and you started over), AMS purge waste on multi-color prints, and support material that you remove and discard. Each of those needs its own treatment. Failures get amortized in the Failure Rate Calculator. AMS purge has a dedicated AMS Purge Waste Calculator. Support material is usually small enough to fold into your waste percentage.

Material-specific waste rates

Different filaments waste differently. Use these as starting points and adjust based on what your printer actually does.

If you keep your filament dry and your retraction dialed, you can run lower than these numbers. If you live in humid climate or print fast on a low-end machine, expect higher.

Three real worked examples

To make this concrete, here are three typical hobbyist prints on a Bambu P1S, with the math written out.

That last example shows why multi-color prints can blow your per-print cost. The actual dragon weighs 320 g, but the math says you spent material on 500 g of filament. Half your spool can vanish on purge for a single show-piece print.

Common mistakes that throw the number off

1. Using length, not weight. Slicers can show estimated meters or grams. Use grams. If you only have meters, multiply by density (PLA: ~3.0 g/m, PETG: ~3.2 g/m, ABS: ~2.8 g/m for 1.75 mm filament).
2. Forgetting the spool weight. A "1 kg" spool often refers to filament weight, not the whole package. But some retailers list the gross weight including the plastic spool itself (200 to 300 grams of plastic). If the spec sheet says 1.2 kg gross, you have 1 kg of filament; convert accordingly.
3. Pricing in the wrong currency. European spools are often quoted including VAT, US spools usually not. A €25 spool with VAT included is roughly $24 USD without VAT, not $27.
4. Ignoring sale prices vs sticker prices. If you buy filament during a Bambu Black Friday or Polymaker stock-up sale, your real per-kg cost can be 30 to 40 percent below what the spool retails for. Average across what you actually pay over a year, not the box price.
5. Treating the calculator's number as final. This estimates material cost only. To price a sale piece on Etsy or Patreon, multiply by 3 to cover wear, electricity, and your time. The full breakdown lives in the cost-breakdown guide.

When this estimate is wrong

The calculator is accurate to within a few percent for clean, completed prints with reasonable settings. It will mislead you in three situations:

• Multi-color prints with heavy purging. Use the AMS Purge Waste Calculator to add the purge cost on top. The two numbers combined are the real material cost.
• Frequent failures. If you fail 1 in every 5 prints, your effective per-print cost is 25% higher than what shows here. The Failure Rate Calculator handles this.
• Wet filament or off-spec material. Wet PETG can string so badly that your effective waste hits 15%. If your prints look fuzzy and break easily, your waste factor is higher than the table above.