Filament Weight Calculator

Filament weight depends on cross-section area, length, and material density. Volume = π × (diameter/2)² × length; weight = volume × density. PLA is about 1.24 g/cm³; PETG about 1.27; ABS about 1.04.

Slicer software estimates weight from the 3D model, but this calculator helps when you measure partial spool usage by length or weigh scraps on a scale.

Example: 10 meters of 1.75 mm PLA weighs about 30 g. A 1 kg spool of 1.75 mm PLA holds roughly 330 meters.

Because the cross-section is a circle, weight per metre scales with the square of diameter. That makes 2.85 mm filament about 2.65 times heavier per metre than 1.75 mm, so a 1 kg spool of the thicker material holds roughly 125 metres against about 330 metres of the thinner one. Never reuse a length-per-spool figure across diameters.

Density is the input people get wrong, and it varies by more than the material name suggests. PLA sits near 1.24 g/cm³ and PETG near 1.27, but filled variants change the picture entirely: carbon-fibre and glass-filled blends run higher, while foaming or lightweight PLA can drop below 1.0 and is designed to vary with temperature. Use the vendor's published figure when quoting.

Diameter tolerance quietly shifts the result. Quality filament is specified at ±0.02 mm, but a spool running consistently at 1.79 mm instead of 1.75 mm carries about 4.6% more material per metre — enough to explain a discrepancy between a slicer estimate and a scale reading without anything being wrong.

To measure what is left on a partial spool, weigh the whole thing and subtract the empty spool mass, which is usually printed on the label or the manufacturer's spec page and typically runs 180 to 250 g for plastic spools. Then solve for length from weight; guessing spool mass is the main source of error in remaining-filament estimates.

For job costing, the slicer's figure is the one to trust because it accounts for perimeters, infill, supports, brim, and purge, none of which this calculation knows about. Use this tool for spool inventory, scrap reconciliation, and sanity-checking a slicer estimate that looks implausible.

Material density varies by brand and color — use the filament vendor spec sheet grams per cubic centimeter when pricing jobs, not a generic PLA assumption alone.

Support structures and raft material add grams beyond part volume — include slicer support preview totals when quoting customer jobs.