Filament Usage Calculator (3D printing)

Filament is a long cylinder of known diameter, so volume = pi * r^2 * length, where r is the cross-section radius. Multiplying volume by material density gives mass. The calculator converts the radius from mm to cm and length from m to cm so mass comes out in grams.

Mass depends on the cross-section area, which is proportional to the radius squared. A 2.85 mm filament has a much larger cross-section than 1.75 mm, so the same length weighs more. Choosing the right diameter is essential for an accurate estimate.

PLA is about 1.24 g/cm3, PETG about 1.27, ABS about 1.04 and TPU about 1.21 g/cm3. Filaments with additives (carbon fibre, metal) have higher density. The calculator defaults to 1.24 g/cm3 for PLA, but the value can be changed.

The spool percent shows what fraction of a standard 1 kg (1000 g) spool the print uses. A result of 5% means 50 g, one twentieth of the spool. It is a handy way to estimate how many prints you get from one roll.

Slicers such as Cura, PrusaSlicer or Bambu Studio report the predicted filament length and mass after slicing. If you only know the length, this calculator converts it to mass, which helps when comparing materials of different density.

It simply converts the given length to mass and does not know how much goes to the model versus supports or raft. To include them, enter the total filament length reported by your slicer, which covers all additional structures.

It depends on print size. A 1 kg PLA spool is about 330 metres of 1.75 mm filament. Small parts use a few grams, large models hundreds of grams. The spool percent makes it easy to estimate how many prints fit on one roll.

No. The cross-section of 2.85 mm is about 2.65 times larger than 1.75 mm (ratio of squared diameters), so a metre of thicker filament weighs proportionally more at the same density. That is why you must know the diameter.

Yes, filament mass is the basis for pricing. Multiply mass in grams by the filament price per gram (spool price divided by its mass). A full quote should also include energy, printer depreciation, labour, failed prints and margin.

The result estimates an ideal, uniform filament with constant diameter and given density. In practice diameter has tolerances (e.g. +/-0.02 mm) and density may vary between batches. For critical uses, weigh the actual print on a precise scale.