Filament Remaining on Spool
Weigh the spool and subtract the empty weight, or measure the diameter of the remaining filament. Either way you get grams, metres and whether the next print will make it.
How it's calculated
by weight: remaining = gross weight − empty spool weight
by diameter: volume = π × (outer² − core²) / 4 × width × packing factor
remaining grams = volume (cm³) × density- Weighing is exact if you know the empty spool weight. We list the common ones; print the spool brand's weight on a label for next time.
- Measuring works without a scale: the filament forms a hollow cylinder between the hub and the outer layer. Random winding leaves gaps, so a packing factor (about 0.7) corrects for air.
- The “will my print finish?” check compares the remaining grams with what your slicer needs, plus a safety margin for purge and waste.
Questions people ask
How much does an empty Bambu Lab spool weigh?
The bare reusable plastic spool weighs about 213 g. Filament that ships on it is wound on a 40 g cardboard core, so a factory spool reads about 255 g once empty and about 1,255 g when full. A refill core alone is about 40 g.
How much does an empty filament spool weigh in general?
Plastic spools: roughly 125–250 g (older black spools 200–250 g, modern thin ones 125–160 g). Cardboard spools: 125–175 g. Check the brand list in the tool for exact figures.
How accurate is the diameter method?
Within about ±15%, because winding density varies. It is good enough to decide whether to start a 200 g print on a spool that looks half full.