Filamento: comprimento → peso

3D printing filament: length to weight

3D-printer filament is sold by mass (usually 1 kg spools), yet slicers report usage in meters. To bridge the two, treat the filament as a cylinder: weight = π · (d/2)² · length · density, where d is the filament diameter and density comes from the material. Typical values run PLA 1.24 g/cm³, ABS 1.04, PETG 1.27, nylon 1.14, TPU ~1.20. As an example, 1 m of 1.75 mm PLA weighs about π · 0.0875² · 100 · 1.24 ≈ 2.98 g, which means a 1 kg PLA spool holds roughly 1000 / 3 ≈ 333 m of filament. Brazilian standard ABNT NBR 17068 covers FFF/FDM filament dimensions and quality.

Applications

Handy for budgeting print jobs, since Cura, PrusaSlicer and Bambu Studio report meters and this turns that into grams and cost. It lets you track a remaining spool with no scale around (measure the leftover length and convert), and it helps when you compare materials, because PETG is denser than ABS and the same model ends up heavier. You can also plan multi-spool prints by checking whether the filament you have left will see the job through.

FAQ

Why does my slicer estimate differ? Slicers also fold in purge, prime lines and supports. The formula gives you raw filament, while the slicer reports total spool consumption.

What about 2.85 mm filament? Same formula, just plug in d = 2.85. Its cross-section is about 2.65× larger than 1.75 mm, so each meter weighs that much more.

Is the density on the spool label exact? Think of it as an average. Pigments, fillers like wood, metal or carbon fiber, and even humidity nudge the density by a few percent. When the budget is tight, weigh a known length and work out the real density yourself.