How it works
cost per gram = spool price ÷ spool weight. grams per meter = density × π × (diameter ÷ 2)². print cost = cost per gram × print weight. length = weight ÷ grams per meter.
Filament is priced by weight but printed by length, and this tool moves between the two. Cost per gram is the simplest number: spool price divided by the net grams on the spool, so a $25 kilogram spool is 2.5 cents a gram, and a 50 g print is about $1.25 of plastic. To convert grams to meters you need the filament’s density and diameter, because a filament is just a solid cylinder. Its mass per meter is the density times the cross-sectional area (π times the radius squared) times the length. For 1.75 mm PLA at 1.24 g/cm³ that works out to about 2.98 grams per meter, so a kilogram spool holds roughly 335 meters; 2.85 mm filament is far thicker, so the same kilogram is only about 125 meters. The calculator uses a published density for each material — PLA 1.24, PETG 1.27, ABS 1.05, ASA 1.06, TPU 1.23 and Nylon 1.14 g/cm³ — but real filament varies by brand and grade, so treat the length figures as close estimates rather than exact counts.
Sources
- PLA density 1.24 g/cm³ Brăileanu et al. (2025). Structure and Texture Synergies in FDM Polymers. Polymers, 17(15), 2159 (MDPI, open access). Table 1 lists PLA density 1.24 g/cm³.
- PETG density 1.27 g/cm³ Tunçel, Kahya & Tüfekci (2024). Optimization of Flexural Performance of PETG Samples Produced by FFF. Polymers, 16(14), 2020 (MDPI, open access): PETG filament density 1.27 g/cm³.
- ABS 1.05 and TPU 1.23 g/cm³ Thavornyutikarn et al. (2023). ABS/TPU Blends for Material Extrusion 3D Printing. ACS Omega, 8(47), 45013–45025 (open access): ABS density 1.05 g/cm³, TPU density 1.23 g/cm³.
- ASA density 1.06 g/cm³ Bolat et al. (2025). Hardness and Surface Roughness of 3D-Printed ASA Components. Polymers, 17(21), 2881 (MDPI, open access). Table 1: ASA filament density 1060 kg/m³ = 1.06 g/cm³.
- Nylon (PA6) density 1.14 g/cm³ Farina et al. (2019). High-Performance Nylon-6 Sustainable Filaments for Additive Manufacturing. Materials, 12(23), 3955 (MDPI, open access): Nylon-6 specific weight 1.14 g/cm³.
- Weight↔length geometry A filament is a solid cylinder: mass per unit length = density × cross-sectional area, with area = π × (diameter ÷ 2)². Cost per gram = spool price ÷ net spool weight.
FAQ
How much does a 3D print cost in filament?
Multiply the print’s weight in grams by your cost per gram. Cost per gram is just the spool price divided by the grams of filament on the spool: a $25 one-kilogram spool is 2.5 cents per gram, so a 50-gram print costs about $1.25 in plastic. That is only the material, though — for the full picture add electricity, machine wear, failed prints and labor with the 3D printing cost calculator.
How many meters of filament are on a spool?
It depends on the material and the diameter. A one-kilogram spool of 1.75 mm PLA holds roughly 330–335 meters, because 1.75 mm PLA weighs about 2.98 grams per meter. Denser materials like PETG give slightly fewer meters per kilogram, and 2.85 mm filament is much thicker, so the same kilogram is only about 125 meters. Enter your spool weight and the calculator shows the length for the material and diameter you pick.
How do I know how much filament is left on a spool?
Weigh the spool, subtract the empty reel’s weight (often printed on the spool or listed by the maker), and you have the grams of filament remaining. Enter that in the “filament left” field and the calculator converts it to meters, so you can tell at a glance whether there is enough for the next print. Weighing is far more reliable than guessing from how full the reel looks.
Does filament density really matter for cost?
For cost per gram, no — you pay by weight regardless of density. Density matters when you convert between weight and length, or compare materials by volume. A denser filament like PETG weighs more per meter than PLA, so a spool of the same weight holds fewer meters, and a print of the same volume weighs more and therefore costs more. That is why the calculator uses a specific published density for each material.
Why do the densities differ slightly from my spool’s spec?
Filament density is not a single universal constant; it varies with the exact polymer grade, colourants, fillers and how the filament is made, typically by a few hundredths of a gram per cubic centimetre between brands. The values here come from peer-reviewed measurements of real filaments and are representative, but if your supplier publishes a density for your exact spool, that figure will be marginally more accurate for length estimates.
Estimates only. Length figures assume the published density for each material; real filament varies by brand, grade and colour, so weigh your spool for the most accurate remaining-length figure. Material cost excludes electricity, machine wear and labor.