Filament Spool Remaining Weight Calculator
Find how many grams and meters of filament are left on a spool by weighing it.
Check if the spool will last for your next print before you start a long job.
The easiest way to know how much filament is left on a spool is to weigh it on a kitchen scale. Subtract the spool’s tare weight (the weight of the empty spool itself) and you have the mass of filament remaining.
Common tare weights. Spool tare weights vary by brand and material, but typical values are:
- Most 1 kg spools: 180-250 g (commonly around 220 g for cardboard, 230-280 g for plastic spools)
- Bambu Lab spools: ~150 g
- Polymaker and eSUN cardboard spools: ~120-150 g
- Empty Prusament spools: ~185 g
- Heavy-duty industrial spools: can exceed 400 g
If you do not know the tare weight, weigh the spool before loading it into the printer on first use. Write it on the spool with a marker.
Converting mass to length. Given filament diameter d and material density rho:
length (m) = mass (g) / (rho (g/cm³) x pi x (d/2)² (cm²) x 100)
Simplified for 1.75 mm PLA (rho = 1.24 g/cm³): length (m) = mass (g) / 2.98
For 2.85 mm PLA: length (m) = mass (g) / 7.89
The runout check. Enter the estimated print weight from your slicer (usually shown as grams in the print info). If remaining filament minus estimated print weight is below about 20 g, plan a filament swap — slicer estimates can be off by 10-15%.