Technical context
For identical jobs, divide usable net mass by total mass per job and round down. For mixed jobs, maintain a consumption ledger. A spool with a known mass can also be expressed in length, but that conversion requires diameter and material density.
How many complete jobs fit on 1 kg?
View data table
| Comparison | jobs |
|---|---|
| 25 g | 40 |
| 50 g | 20 |
| 100 g | 10 |
| 150 g | 6 |
Practical workflow
Twenty 50 g parts theoretically exhaust 1,000 g with no reserve. If each job also uses 5 g for supports and setup, only eighteen whole jobs fit. A production allowance further reduces promised output; the end-of-spool sensor does not create missing material.
Calculation and units
Jobs = floor((available ? reserve)/grams per job); usable leftover = available ? reserve ? jobs × grams per job.
Worked example
980 g stock ? 20 g reserve allows eleven jobs at 85 g, leaving 25 g usable. Rounding up wrongly promises a twelfth job.
Validate the outcome
Calculate each color separately. Combined mass can hide that a specific color runs out first.
Hours, meters and parts are different answers
A kilogram can be expressed in strand length once diameter and density are specified, but that does not establish printing hours. A low-flow miniature can consume material slowly while taking considerable time for tiny layers. A large thick-wall part can consume the same stock much faster. To estimate hours, use the known consumption rate of a relevant job rather than a universal spool lifetime.
To estimate parts, use whole-job grams and round down to complete units. Decide whether shared setup extrusion is per plate or per object. Ten objects printed together may share a single skirt, while ten separate starts may spend startup material ten times. The practical output depends on that production strategy.
A realistic 1 kg production example
Suppose a recurring part consumes 45 g useful plastic, 8 g support and 2 g startup extrusion per separate job. Total is 55 g. Holding back a 25 g reserve leaves 975 g usable, enough for seventeen complete jobs and 40 g usable remainder. Counting only the 45 g object would suggest twenty-one complete jobs with the same reserve, overpromising four jobs.
If the work has a failure rate, do not describe those seventeen attempts as seventeen guaranteed accepted pieces. Stock planning and accepted yield are separate. Record the typical material consumed before failure detection and evaluate expected reprint demand using the failed-print model. For a customer commitment, use a cautious inventory buffer appropriate to your evidence.
Manage partial spools without guessing
Keep an inventory record with spool identity, measured tare, net remaining mass and material profile. Spools of different designs can have different empty weights even when the labels both say 1 kg. A visually half-full spool is a poor stock measurement because winding geometry and core diameter affect its appearance. Weighing is generally more useful than estimating from a photograph.
When combining spool remnants, check material compatibility and the printer's documented runout recovery behavior. Do not assume every machine can pause, unload and resume invisibly. A filament change can leave a seam or color difference that matters to the customer's finish requirement, even if the job technically completes.
Spool output with25 g reserve
| Counted demand | Per job | Whole jobs from975 g |
|---|---|---|
| Object only | 45 g | 21 |
| Object support and setup | 55 g | 17 |
Turn mixed work into a stock ledger
For mixed jobs, subtract each complete consumption from measured stock rather than assigning a universal parts count. Preserve spool identity and tare; a 1 kg label identifies nominal net purchase quantity, not current loaded weight. After a substitution, remeasure and keep a consistent reserve rule. Plan per color or material and account for the visible effects of runout recovery, because finishing successfully does not guarantee an invisible seam.
How many printing hours is one spool?
There is no fixed conversion. Hours depend on the relevant job's extrusion rate, travels, acceleration, layer cooling and profile. A kilogram is enough for a mass-based stock calculation; to estimate hours, use actual duration and consumption of representative work. Dividing meters by requested toolhead speed is invalid because toolhead travel distance is not filament feed length.
Can the last grams be used without reserve?
Possibly, but exact equality between reported need and measured stock is fragile. Tare error, scale uncertainty, profile density and unreported priming can make the estimate wrong. A reserve is a declared planning choice, not proof that a fixed percentage fits every printer. If relying on runout recovery, confirm the documented behavior and the finish requirements for a mid-job change.