Compare up to three spools by price and weight to find which is genuinely the best value — and what a gram of each material really costs you.
| Spool A — cost per gram | — |
| Spool B — cost per gram | — |
| Spool C — cost per gram | — |
| Best value | — |
| Cost of one print (best spool) | — |
| You save per print vs worst | — |
Filament is sold in several sizes — 250 g samples, 500 g half spools, 1 kg reels and 3 kg bulk reels — and the sticker price tells you almost nothing on its own. A $18 spool looks cheaper than a $22 spool until you notice it holds 750 g rather than a full kilogram.
cost per gram = spool price ÷ filament weight in grams
Run the three defaults above and the ranking flips. Spool A at $22 for 1000 g costs 2.20 cents per gram. Spool B at $18 for 750 g costs 2.40 cents per gram — nearly ten percent more, despite the lower price tag. Spool C at $55 for 3000 g costs 1.83 cents per gram, the best value of the three, but only if you will actually use three kilograms before it absorbs moisture and goes brittle.
On a 100 g print that is the difference between $1.83 and $2.40 of material — about 31% more per part, on every part, forever, because you bought the spool that looked cheaper.
Weight is not the whole story either, because different materials have different densities. A part printed in ABS weighs noticeably less than the same part in PETG, so a material that costs more per kilogram may not cost more per part.
| Material | Typical price / kg | Density (g/cm³) | Cost per cm³ of part |
|---|---|---|---|
| PLA | $18 – $25 | 1.24 | Lowest for most prints |
| PETG | $20 – $28 | 1.27 | Slightly above PLA |
| ABS | $18 – $26 | 1.04 | Low — very light per volume |
| TPU | $30 – $45 | 1.21 | Roughly double PLA |
| Nylon | $38 – $55 | 1.14 | High price, low density |
Bulk reels are cheaper per gram almost without exception. The question is whether the saving survives three practical costs that do not appear on the invoice.
A reasonable rule: buy in bulk only for the two materials you use most, and only in quantities you will finish within about six months. Everything else in 1 kg spools.
Divide the price you paid by the filament weight in grams, excluding the spool itself. A $22 spool holding 1000 g of PLA costs 2.2 cents per gram. Always use the filament weight, not the shipping weight.
Nearly always, but not universally. Some brands price small spools competitively to attract new customers, and specialty colours are sometimes only available in small sizes. Compare per gram rather than assuming.
Two reasons stack: it costs roughly double PLA per kilogram, and it prints slowly. The slow speed does not change the cost per gram, but it raises the electricity and machine-wear cost allocated to each part, which is why the total cost per part rises more than the material price alone suggests.
No. Both 1.75 mm and 2.85 mm filament are sold by weight, so the cost per gram is comparable. Diameter affects printer compatibility and maximum flow rate, not price per unit of material.