How is cost per gram calculated?

Cost per gram equals the spool price divided by the spool's net filament weight in grams. A 25 dollar / 1000g spool works out to 0.025 per gram. The print cost is then this rate multiplied by your print weight.

Why does the calculator ask for material when I enter length?

Length only converts to weight if it knows the filament's cross-sectional area and density. The diameter (1.75mm or 2.85mm) sets the area and the material (PLA, PETG, etc.) sets the density, so both are needed for an accurate length-to-cost result.

What waste percentage should I use?

A 3-8 percent allowance covers purge lines, prime towers, skirts, and the odd failed first layer. Multi-material prints with frequent tool changes can waste 15 percent or more, so raise the figure if you run a purge tower.

Does this include electricity or machine wear?

No. This calculator covers material cost only. To price a print for sale, add electricity (printer wattage times run time times your tariff), an hourly machine-depreciation rate, and your labour and margin on top.

Is the result accurate for specialty filaments?

Yes for cost, because cost per gram is independent of material. For length-based input the density matters: carbon-fiber and wood-fill blends are slightly denser than pure PLA, which is why those options are listed separately.

3D Print Filament Cost Calculator

The fastest way to know what a print actually costs in material. Enter your spool price and weight once, then drop in the print weight or length your slicer reports and read the cost instantly.

How it works

The core figure is cost per gram:

cost per gram = spool price ÷ spool net weight (g)

A typical 1 kg spool at $25 gives $25 ÷ 1000 = $0.025 per gram. Your print’s material cost is simply:

material cost = print weight (g) × cost per gram × waste factor

The waste factor accounts for purge lines, skirts, prime towers, and failures — a 5% allowance multiplies the weight by 1.05.

Working from length instead of weight

Some slicers report filament used as a length. To convert length to weight the calculator needs the strand’s cross-sectional area and the material density:

area (cm²) = π × r², where r is the filament radius in cm (1.75mm → 0.0875cm)
volume (cm³) = area × length (cm)
weight (g) = volume × density

PLA has a density of 1.24 g/cm³; PETG 1.27; ABS 1.04. Pick the right material and diameter and the length-to-cost conversion stays accurate.

Tips and example

A 30g PLA print from a $25 / 1kg spool with a 5% waste allowance:

cost per gram = $0.025
effective weight = 30 × 1.05 = 31.5 g
material cost = 31.5 × $0.025 ≈ $0.79

To price a print for sale, treat this material cost as your floor and layer on electricity, machine depreciation, post-processing time, and margin. Everything runs locally in your browser — no spool or print data leaves your device.