Why we sort by price per kilogram
Filament comes in spools of 250 g, 500 g, 1 kg, 2 kg, and 3 kg+. A "$15 spool" could be a great deal or a terrible one depending on how much filament is actually in it.
The math
Price per kg = spool price × 1000 ÷ spool weight in grams.
So a $14.99 spool of 500 g works out to $29.98 / kg, while a $19.99 spool of 1 kg works out to $19.99 / kg. The "cheaper" $14.99 spool is actually 50% more expensive per gram of filament.
What FilamentMonkey does
Every deal card on this site shows the spool price and the
computed price per kg, side by side. The default sort on the home page
is best-ppk — lowest price per kg first. You can also sort by
lowest spool price, biggest discount, highest rating, or newest.
When price per kg isn't the right metric
- Color matching: if you need exactly one color for a specific project, a more expensive spool that ships in time may be worth it.
- Shipping costs: not factored into our price per kg. Amazon Prime shipping is usually free; a non-Prime listing might not be.
- Brand reputation: cheap unknown-brand filament can clog hot-ends. Pay a little more for proven brands until you've found one you trust.
Spool size guidance
- 250 g: sampler / accent color. Almost always the worst per-kg rate.
- 500 g: reasonable for low-volume hobbyists or for trying a new color before committing.
- 1 kg: the sweet spot for most printers. Default view on our home page filters to 1 kg.
- 2 kg / 3 kg: best per-kg rate when you print constantly with a single color. Watch out for storage humidity.