Filament Density and Weight: PLA vs. ABS vs. PETG
How to convert filament volume to weight using density, typical density values for PLA, ABS, and PETG, and weight per meter for 1.75mm filament.
What is filament density, and why does it matter?
Density (g/cm³) measures how much a given volume of resin weighs. A slicer typically reports volume, not weight, so estimating material cost or how much filament remains on a spool means multiplying that volume by the material's density. Since density varies by resin type, the same printed volume weighs a different amount depending on what it's printed in.
How density differs across PLA, ABS, and PETG
As representative published figures, PLA runs roughly 1.24 g/cm³, ABS roughly 1.04 g/cm³, and PETG roughly 1.27 g/cm³. A part of identical volume comes out lighter in ABS than in PLA or PETG. Values shift slightly between brands of the same material, so check a datasheet for a precise estimate.
The formula for converting volume to weight
Weight in grams equals volume in cm³ times density in g/cm³. A 50 cm³ part printed in PLA (1.24 g/cm³) weighs 50 x 1.24 = 62 g, while the same volume in ABS (1.04 g/cm³) weighs 50 x 1.04 = 52 g -- a 10 g difference, about 16%, from switching material alone.
Estimating weight from filament length
Knowing the filament's diameter (commonly 1.75 mm) lets you get volume from cross-sectional area times length. A circle with radius 0.0875 cm has an area of pi x 0.0875^2, about 0.0241 cm², so 1 meter (100 cm) of filament has a volume of roughly 2.41 cm³. Multiplying by PLA's density of 1.24 g/cm³ gives about 2.98 g per meter.
Why the same length weighs differently by material
The 1.75 mm diameter is standard across materials, but density isn't, so weight per meter varies. Using that same cross-sectional volume (about 2.41 cm³/m), PLA comes out to roughly 2.98 g/m, ABS to roughly 2.50 g/m, and PETG to roughly 3.06 g/m. Printing the same length in a different material changes how much weight you actually use.
A common mistake in density conversions
A frequent error is reusing PLA's density to estimate ABS or PETG weight, which introduces roughly a 19% error. Another is confusing a spool's gross weight, including the empty reel and packaging, with the net weight of filament alone -- always base a remaining-material estimate on the net filament weight.
Frequently asked questions
For the same volume, is PLA or ABS heavier?
PLA. Its density is about 1.24 g/cm³ versus roughly 1.04 g/cm³ for ABS, so equal volumes of PLA weigh about 19% more.
What's the formula for converting volume to weight?
Weight (g) equals volume (cm³) times density (g/cm³).
How much does 1 meter of 1.75mm filament weigh?
It depends on the material. Multiplying the cross-sectional volume (about 2.41 cm³/m) by density gives roughly 2.98 g for PLA, 2.50 g for ABS, and 3.06 g for PETG.