By construction, not by brand:
| Reel type | Empty weight | Typical examples |
|---|---|---|
| Cardboard, 1 kg | 140–180 g | Polymaker cardboard, Bambu refill reels, Eryone |
| Injection-moulded plastic, 1 kg | 180–250 g | eSun, Sunlu, Overture, most budget lines |
| Prusament, 1 kg | 195–210 g | printed on the label of every reel |
| Cardboard, 500 g | 90–130 g | sample and trial spools |
| Plastic, 500 g | 110–170 g | TPU samples, engineering-material half-reels |
| Refill coil | none | MasterSpool refills, Bambu and Polymaker refill coils |
The half-kilogram reels are the bad deal
A 500 g plastic reel weighs 110 to 170 g — nearly as much as a 1 kg one, for half the filament. If you are paying shipping by weight, or storing a lot of specialty materials in small quantities, the packaging is a real fraction of what you are buying.
Refill coils remove that entirely. They also remove the guesswork: with no reel to subtract, the gross weight on the scale is the filament weight.
Why these are ranges rather than numbers
Reel weight varies by batch and, on some brands, by colour — the pigment in a moulded reel is not free. Cardboard reels vary more still, because they absorb humidity from the room they are stored in.
So every figure above is a fallback for when you have nothing better. What you actually want is your own reel, weighed once, with the number written on it.
What it changes
The whole point of the table is that it sits between you and an estimate of remaining filament. Guess a cardboard reel when you have a heavy plastic one and you overestimate by up to 110 g — roughly thirty-seven metres of 1.75 mm PLA, and quite enough to run out mid-print.
Packaging mass has been falling steadily as brands move to cardboard and refills, so old rules of thumb about "about 250 g for a spool" are now wrong more often than right. If you learned a number years ago and have not re-weighed since, it is probably too high for whatever is on your shelf today.
Subtract your own reel figure in the length and weight converter, or see the brand detail in the spool weights guide.