How to weigh what is left
Take the spool out of the printer, the feeder or the dryer, and set it on a kitchen scale. Take off the weight of the empty spool, and what remains is the filament. A scale that reads to the gram is plenty, since a meter of 1.75 mm PLA weighs about 3 g.
Pick the empty spool from the list, or type the weight of an empty spool you weighed yourself. The calculator also turns the grams into meters for the material you choose, so you can check them against what a print needs.
The printer’s own estimate
A printer that reads a spool’s tag shows how much is left, but it does not weigh the spool. We watched one Bambu Lab AMS move its estimate for a new 1 kg spool of PETG between 91% and 100% during a print that used 91.7 g. It ended at 98%, or 980 g, while the slicer’s grams left about 908 g. A scale and the weight of the empty spool give the real figure.
About the weights in the chart
The weights come from people who weighed their own empty spools and posted the numbers: members of the Bambu Lab, Prusa and 3DPrintingSpace forums between 2021 and 2024, and Gough Lui’s notes from 2022. Where two people weighed the same spool differently, the chart keeps both numbers.
The Bambu Lab rows cover its reusable spool and its high-temperature spool, with and without its cardboard core. The eSun rows show how much one brand varies: from 203 g for a clear half-kilogram spool to 230 g for a black kilogram one.
Keep your own number
When a spool runs out, weigh it empty and write the number on its side. Next time you buy that filament, you have the exact weight to type into the calculator.
Between two weighings, a filament tracker takes the slicer’s grams of each print off the spool, so you know roughly what is left without a scale.