How many prints do you get from one kilogram of filament?

At 40 g a print — a reasonable average for household and functional parts — a kilogram gives 25. At 15 g, the mass of a Benchy, it gives 66.

The arithmetic is trivial. The input that decides it is your own average part mass, and most people overestimate theirs badly.

Why the average is lower than it feels

Memorable prints are big ones. Day-to-day printing is mostly small: brackets, clips, adapters, organisers, replacement knobs, test pieces. A spool disappears into dozens of forgettable objects rather than a handful of impressive ones.

The way to find out is to look, not to guess. Most slicers log the mass of every job; a month of that log divided by the number of prints is a real figure, and it will beat any estimate on this page.

Three things that shrink the number

• Failures. At a 20% scrap rate you get four fifths of the count above, and the failures are drawn from the same kilogram.
• Purge, prime and skirts. Individually negligible, collectively a real slice across forty or more prints.
• The unusable tail. Filament wound closest to the hub takes a tight curve that many extruders refuse, so a spool is finished in practice some way before it is finished on paper.

Between them, treat the table as a ceiling and expect to land somewhat under it.

The multi-colour exception

A purge tower changes the picture completely. A tall four-colour print can put more plastic into the tower than into the model, which means the same kilogram yields a fraction of the parts a single-colour workflow would give.

If you print multi-colour regularly, count the tower as a part. It has a mass and it comes out of the same spool — and unlike the parts, it goes straight in the bin.

The same logic applies, more mildly, to any workflow with a lot of supports. Two identical spools can yield very different numbers of finished objects depending on how much of each print is scaffolding.

Divide any spool by any per-print mass in the length and weight converter.