Price per kilogram tells you what the spool cost. Price per cubic centimetre tells you what the part costs, and those rank materials differently because density varies by more than three to one across this site's data.
| Material | Density | Spool price | Per cm³ of part |
|---|---|---|---|
| ABS | 1.05 g/cm³ | $24/kg | $0.025 |
| PLA | 1.24 | $22/kg | $0.027 |
| PETG | 1.27 | $24/kg | $0.030 |
| TPU 95A | 1.2 | $35/kg | $0.042 |
| PA6 | 1.14 | $50/kg | $0.057 |
| Polycarbonate | 1.2 | $55/kg | $0.066 |
| Metal-filled PLA | 3.2 | $70/kg | $0.224 |
Why the ranking shifts
ABS and PLA sell for close to the same money per kilogram, but ABS is the lighter polymer — 1.05 against 1.24 g/cm³ — so a given object costs about a sixth less to make in ABS. On the shelf they look identical; in the part they are not.
The dramatic case is metal-filled PLA. At 3.2 g/cm³ it is nearly three times as dense as plain PLA, so its already-high spool price is multiplied again in the part. Twenty-two cents a cubic centimetre is eight times PLA's figure for the same geometry.
When to use which figure
- Per kilogram — buying spools, comparing suppliers for the same material.
- Per gram — costing a specific print, because the slicer reports mass.
- Per cubic centimetre — choosing between materials for a part whose shape is fixed.
The third is the one almost nobody calculates and the one that answers "would this be cheaper in something else". It is also the honest way to read a spool that claims to be a bargain: a cheap dense filament and an expensive light one can meet in the middle once the comparison is by volume.
A caveat about the density figures
Each of the numbers above is a single representative value from a range. Real PLA runs from 1.17 to 1.26 g/cm³ and metal-filled from 2 to 4, so treat the table as a ranking rather than a quotation. A matte PLA with mineral filler behaves like a different material for this purpose entirely.
Compute the figure for your own spool by entering its price and its density in the print cost calculator, and check densities on the materials index.