Weigh your loaded spool, enter its empty-spool tare, and set aside a filament reserve. This calculator estimates how many identical print jobs fit within the usable mass and how much filament remains afterward. All mass inputs and results use grams (g).
Enter the combined weight of the spool and its remaining filament. Use an empty-spool tare measured for the same spool or a matching spool; account consistently for removable holders or accessories. The loaded weight must be at least the tare.
Choose a reserve between zero and the filament currently present. The reserve is set aside once for the spool, not once per job. Enter the slicer’s filament-only mass for one complete job. Include supports, brims and other printed structures in that estimate where applicable. Additional waste covers only material not already included in the slicer estimate, avoiding double counting.
Inputs accept 0.01 g increments up to 100,000 g. Slicer mass must be at least 0.01 g; other inputs may be zero. These are calculator limits, not claims about scale accuracy. A tare greater than loaded weight, or a reserve greater than available filament, makes dependent results unavailable rather than reporting zero jobs. Correct those measurements before using the estimate.
Prusa’s filament-checking demonstration describes estimating remaining filament from measured spool-plus-filament weight and spool information. Here, subtracting the empty spool gives filament mass directly; no length or density conversion is needed.
The reserve, per-job allowance and remaining-mass equations are direct mass accounting for this calculator’s stated assumptions. Each identical job consumes S + W grams. The job count rounds downward before calculating consumption and leftovers. The Python mathematical reference documents the floor operation used in this derivation.
The estimate assumes fixed consumption per job and excludes failed jobs or other unentered losses. A job means the complete slicer job, which may contain several objects. Slicer estimates, scale readings and tare values can differ from actual consumption; choose a reserve appropriate to your measurements. Display rounding does not determine the job count.
| Scenario | Loaded / tare / reserve | Slicer / extra waste | Usable mass | Whole jobs | Usable leftover | Total filament left |
|---|---|---|---|---|---|---|
| Default example | 750 / 200 / 25 | 60 / 5 | 750 − 200 − 25 = 525 | floor(525 ÷ 65) = 8 | 525 − 8 × 65 = 5 | 25 + 5 = 30 |
| Exact fit above reserve | 500 / 200 / 20 | 65 / 5 | 280 | floor(280 ÷ 70) = 4 | 0 | 20 |
| Insufficient usable mass for one job | 250 / 200 / 20 | 35 / 5 | 30 | floor(30 ÷ 40) = 0 | 30 | 50 |
| All remaining filament reserved | 225 / 200 / 25 | 10 / 0 | 0 | 0 | 0 | 25 |
Use the Filament Length to Weight Calculator when your starting measurement is length rather than mass.
Sources
- Prusa 3D — Check filament length on your Prusament spool: measured loaded-spool weight and spool information.
- Python documentation — math.floor: mathematical basis for rounding down to whole jobs.
Production flag: create and register a 400 × 400 pixel WebP thumbnail before activation. No registered thumbnail asset was supplied. Depict the cheerful yellow five-point star mascot floating with hands and no separate legs or feet, beside a filament spool, weighing scale and small printed objects. Use a white background with navy, blue and teal educational graphics. Inspect neighboring tool thumbnails for visual consistency, then add the registered asset as the first image block.