3D Print Filament Cost by Weight Calculator
Work out what a 3D print costs in filament from the model weight, spool price and spool size — including waste for supports, brim and purge.
How it works
Cost per gram = spool price ÷ spool grams · Gross grams = model grams × (1 + waste%) · Cost = gross grams × cost per gram
Filament is sold by the spool but consumed by the gram, so the real unit cost is the spool price divided by the net grams on the spool. Your slicer reports the model weight, but the printer also lays down supports, a brim or skirt, and purges filament at tool changes — a waste allowance folds that in. Multiplying the padded weight by the per-gram cost gives the material cost of the print, before electricity or wear.
Worked example
A $22 spool holds 1,000 g, so filament costs $0.022 per gram. A 45 g model with an 8% waste allowance uses 45 × 1.08 = 48.6 g, so the print costs 48.6 × $0.022 = $1.07 in filament.
Frequently asked questions
Does this include electricity and printer wear?
No — this is filament cost only. Electricity for a multi-hour print is usually a few cents, and nozzle or belt wear is spread across thousands of prints, but if you sell prints you should add a small margin for both plus your time.
What waste allowance should I use?
For simple models with little support, 3–5% covers the brim and purge. Tall or overhanging models that need heavy supports can waste 20% or more, and a first-attempt failure rate pushes it higher still.
Why use net spool weight instead of the box weight?
A "1 kg spool" means 1 kg of plastic; the cardboard or plastic reel adds 150–250 g on top. Dividing the price by the net filament weight keeps the per-gram cost accurate.
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This calculator is for educational purposes. Double-check important results before acting on them.