Your slicer calculates the volume of plastic it will extrude. To show grams, it multiplies by the density set in the filament profile. If that density is wrong, the gram figure is wrong — and so is any cost estimate built on it.
Density of common filaments
| Material | g/cm³ | Metres per kg (1.75 mm) |
|---|---|---|
| PP | 0.90 | 462 |
| Nylon PA12 | 1.01 | 412 |
| ABS / HIPS | 1.04 | 400 |
| ASA | 1.07 | 389 |
| Nylon PA6 | 1.14 | 365 |
| TPU 95A | 1.21 | 344 |
| PLA | 1.24 | 335 |
| PETG | 1.27 | 327 |
| Matte PLA | 1.30 | 320 |
A kilogram of ABS is almost 400 m of filament; a kilogram of PETG is 327 m. For the same part, ABS uses 18% fewer grams. Compare spools per metre, not per kilogram — the cost per gram and metre tool does this.
Why the figure on the spool matters
Filled filaments vary a lot. “Wood PLA” ranges from 0.8 g/cm³ (foamed) to 1.4; carbon-fibre blends are 1.26–1.30; matte PLA with mineral filler is around 1.30. Metal-filled PLA can exceed 3 g/cm³, so a 500 g spool is a very short length. Always use the manufacturer’s technical data sheet figure in your slicer profile.
Measuring density yourself
Cut exactly 1 m of filament, weigh it on a 0.01 g scale, and divide by 2.405 (the volume in cm³ of one metre of 1.75 mm filament; 6.38 cm³ for 2.85 mm). Example: 2.98 g ÷ 2.405 = 1.24 g/cm³. The length ↔ weight converter will do the arithmetic with a custom density.