21.8 hours to extrude a whole kilogram of PLA at 0.2 mm layers and 150 mm/s. At a conservative 60 mm/s the same kilogram takes 54.18 hours — two and a half times as long, for identical plastic.
A kilogram of PLA at 1.24 g/cm³ is 806 cm³, so this is really a question about flow rate rather than about spools.
The three regimes
| Setup | Flow | A kilogram takes |
|---|---|---|
| 0.4 mm nozzle, 0.2 mm layers, 60 mm/s | 5.4 mm³/s | 54.18 h |
| 0.4 mm nozzle, 0.2 mm layers, 150 mm/s | 13.5 mm³/s | 21.84 h |
| 0.6 mm nozzle, 0.3 mm layers, 150 mm/s | 27.5 mm³/s, flow limited | 10.77 h |
The third row is the interesting one: the profile asks for 30.6 mm³/s and the hotend caps it at 27.5, so the machine runs slower than commanded and the figure is still barely a fifth of the slow case.
Why the real answer is longer
None of the above includes the gaps. Real printing is punctuated by plate changes, part removal, failed attempts, the print you did not start because you were out, and the spool sitting idle over a weekend.
A machine genuinely running twelve hours a day gets through a kilogram roughly every other day at high flow. A hobby machine used a few evenings a week takes a month or more, which is why filament storage matters more to hobbyists than to farms.
What this tells you about buying
If a kilogram is a fortnight of your printing, buying five spools of a colour you like is committing several months. Filament does not improve while it waits, and hygroscopic materials get measurably worse.
Match the purchase to the throughput. The arithmetic above is the throughput.
The same figure sets a ceiling on what one machine can produce. Even running continuously at high flow, a single printer cannot consume more than about one spool a day — so a workload needing three kilograms a week needs a second machine, not a faster profile.
Run the numbers for your own nozzle, layer height and speed in the print time estimator, or see what the spool costs to consume in 1 kg PLA spool cost.