1,215 g for a full kilogram of filament on a 215 g injection-moulded reel. On a 160 g cardboard reel the same kilogram reads 1,160 g on the scale.
Neither of those is a specification. They are the sum of two things: a payload that really is a kilogram, and packaging that is not standardised at all.
Use it to check what you were sold
Weigh a new spool before you print anything. If it reads 1,215 g and the reel is a 215 g plastic one, you have your kilogram. If it reads well short of that on the same reel, you do not — and that is worth knowing on arrival rather than three weeks later when a print stops short.
Underweight spools do turn up. So do spools where the manufacturer's stated reel weight is optimistic, which produces the same symptom.
The arithmetic that fails
Weighing a part-used spool and subtracting a kilogram. It is intuitive and it is wrong, because the kilogram is the filament, not the package.
Do it on a brand-new plastic-reeled spool and you conclude you have 215 g of filament left when you have 1,000 g. The error is the reel, every time, and it is the single most common mistake in estimating remaining filament.
Expected scale readings by reel type
| Reel | Empty | Full spool reads |
|---|---|---|
| Cardboard, 1 kg | 140–180 g | 1,140–1,180 g |
| Plastic, 1 kg | 180–250 g | 1,180–1,250 g |
| Prusament, 1 kg | 195–210 g | 1,195–1,210 g |
| Refill coil | none | 1,000 g |
Shipping weight is a third number
A boxed spool adds carton, desiccant and sometimes a vacuum bag. That is the figure a courier charges on, and it is why buying four half-reels costs more to ship than two full ones even when the filament is identical.
It also explains why refill coils have spread so quickly. Removing the reel takes roughly a fifth of the shipped mass out of every order, and the buyer keeps one reusable spool instead of accumulating a shelf of empty ones. The trade is that a refill has to be loaded onto a spool before it can be printed, and a coil that unravels on the bench is a genuinely irritating afternoon.
Enter your own gross and reel weight in the length and weight converter.