Reference data
Bambu Empty Spool Weight Chart (by Brand)
What an empty spool weighs, so you can take it off the scale reading and see how much filament is left. A Bambu Lab spool is about 242 g as shipped. Every figure shows its range, where it came from and when it was checked.
The short answer
Most empty 1 kg plastic spools weigh about 200–250 g; cardboard spools are lighter, about 130–165 g. Polymaker states 140 g ± 5% for its cardboard spool, and users report about 242 g for a Bambu Lab spool as shipped. The same brand can vary by 10 g or more, so your own empty spool is the best figure.
filament left = scale reading − empty spool
Example: a Bambu Lab spool reading 742 g holds 742 − 242 = 500 g, about 167.6 m of 1.75 mm PLA.
Empty spool weight table
Sort by any column or filter by brand or spool material. Brand names link to a page with that spool's details and a calculator set up for it.
15 of 15 rows · sorted by spool
The empty weight is the typical value inside the range. “Community readings” are weights reported by owners and collected by the linked source; “Estimate” means no published or reported figure was found.
Brand pages
Why empty spool weights vary
Even within one brand, empty spools differ: makers change spool designs, plastic spools vary from mould to mould, and cardboard takes up moisture from the air, so a cardboard spool kept in a humid room weighs a little more than one fresh out of a dryer. That is why the table shows a range for each brand rather than one exact number. The most reliable empty weight is one you measure yourself.
From grams to length
Volume is mass divided by density, and length is volume divided by the filament's cross-section: L = 4 · m / (π · ρ · d²). For 1.75 mm PLA at 1.24 g/cm³, 1 g is about 0.335 m. 2.85 mm filament has 2.65 times the cross-section, so the same gram gives about 0.126 m.
Bambu Lab AMS spool limits
Bambu Lab's notes for the AMS (checked 24 Oct 2026) say it takes spools 50–68 mm wide and 197–202 mm in diameter. Bambu recommends plastic spools and strongly advises a spool adapter ring for cardboard ones. If you fit a ring, weigh it and add it to the empty weight. The AMS lite has different limits.
When the numbers do not add up
| What happens | Likely cause | What to do |
|---|---|---|
| Runs out mid-print although the scale said 30 g were left | Your empty spool is heavier than the figure used | Weigh an empty spool of the same type and keep a margin before long prints |
| AMS rollers spin but the spool does not turn | Spool outside 197–202 mm across or 50–68 mm wide, or a worn cardboard rim | Fit an adapter ring to cardboard spools or move the filament to a plastic spool |
Empty spools: common questions
Weights, accuracy and the AMS.
What is the empty weight of a Bambu Lab spool?
Owners report about 242 g for a Bambu Lab spool as shipped, with readings from 233 g to 250 g. Use your own empty spool on the same scale when you can: the same brand can vary by 10 g or more.
How much does an empty 1 kg filament spool weigh?
In the table above, plastic spools for 1 kg of filament weigh roughly 200 g to 250 g and cardboard spools roughly 130 g to 165 g. It depends on the brand and even the batch, so the most accurate figure is one of your own empty spools on the same scale.
How do I work out how much filament is left?
Weigh the spool and subtract the empty spool weight. What is left is the filament in grams. To turn grams into length, divide by the filament's density and its cross-section: about 0.335 m per gram for 1.75 mm PLA. The filament calculator does both steps and lets you enter your own empty weight.
Can I use cardboard filament spools in the Bambu Lab AMS?
Bambu Lab recommends plastic spools and strongly advises a spool adapter ring for cardboard ones, to reduce slipping and keep cardboard debris out of the AMS. The spool also has to be 50–68 mm wide and 197–202 mm in diameter. If you fit a ring, weigh it and add it to the empty weight.
Does moisture change the weight of a cardboard spool?
A little. Cardboard takes up moisture from humid air and loses it again in a filament dryer, so its weight can shift by a few grams. If you track filament closely, weigh your empty spool under the same conditions you weigh full ones.
Why does the table say “estimate” for some brands?
We found no published or reported empty weight for those spools, so the figure is a typical value for that kind of spool, not a measurement. Treat it as a starting point and weigh one of your own empties.