Filament length to weight.

Worked example

1.75 mm PLA: cross-section π x 0.875² = 2.405 mm². One metre is 1,000 mm, so its volume is 2,405 mm³ = 2.405 cm³. At 1.24 g/cm³ that is 2.98 g per metre. A 1,000 g spool then holds 1,000 / 2.98 = 335 m. A slicer report of 120 m is 120 x 2.98 = 358 g.

How it works

Filament is a thin cylinder, so its weight is cross-section x length x density. Because 1 mm² x 1 m = 1 cm³, grams per metre equals cross-section area in mm² times density in g/cm³. Larger diameters add up fast: 2.85 mm filament weighs (2.85 / 1.75)² = 2.65 times as much per metre as 1.75 mm.

Typical densities used here are manufacturer data-sheet values: PLA 1.24, PETG 1.27, ABS 1.04, ASA 1.07, TPU 1.21, nylon 1.14, polycarbonate 1.20, PVA 1.23 g/cm³. Real spools vary with brand, colour pigments and fillers, and diameter tolerance (usually ±0.02 to 0.05 mm) shifts the answer by a few per cent. Spool weights usually exclude the spool itself, so a full spool on a scale weighs 150 to 250 g more.

Sources and basis (checked 2026-10-05): cylinder volume geometry; material densities as published on manufacturer data sheets, for example the Prusament materials pages (PLA 1.24, PETG 1.27, ASA 1.07 g/cm³).

FAQ

How many metres are in 1 kg of 1.75 mm PLA?

About 335 metres at a density of 1.24 g/cm3. PETG at 1.27 gives about 327 m and ABS at 1.04 about 400 m.

How many grams is a metre of 1.75 mm filament?

About 2.98 g for PLA, 3.05 g for PETG and 2.50 g for ABS.

Why does my slicer show a different weight?

Slicers use a default density and diameter. Set the density of your filament in the slicer profile to match, and expect small differences from real spool tolerances.

How much does 2.85 mm filament weigh per metre?

About 7.91 g per metre for PLA, which is 2.65 times as much as 1.75 mm filament.

Does the spool weight include the spool?

Usually the label means filament only. A full spool on a kitchen scale weighs more. Weigh an empty spool to find its tare.