395.95 m of 1.75 mm ABS at 1.05 g/cm³, the midpoint of its published band. That is about sixty metres more than a kilogram of PLA gives you, and it is entirely down to density.
ABS is the lightest of the mainstream filaments. Its 1.02 to 1.08 g/cm³ band puts the honest range at 384.96 to 407.60 m, and both ends beat PLA comfortably.
What that means for parts rather than spools
Length per kilogram is the spool-side view. The part-side view is more useful: an identical model printed in ABS weighs about fifteen percent less than the same model in PLA, because the polymer is fifteen percent lighter and the geometry has not changed.
So an ABS spool builds more objects than a PLA spool of the same nominal weight. On material alone, ABS is better value than its shelf price suggests.
Why you will not see that saving
Warping. ABS contracts 0.4 to 0.8% as it cools while its first layer is welded to a hot plate, which is why an enclosure is required rather than helpful. A scrap rate high enough to cancel a fifteen percent material advantage is not hard to reach on an open-frame machine.
The extra sixty metres is real. Keeping it depends on the enclosure, the draught-free room and the bed adhesion, not on the spool.
Larger diameters
In 2.85 mm, a kilogram of ABS is 149.29 m — the same mass through a cross-section 2.65 times larger. One metre of 2.85 mm ABS weighs 6.7 g against 2.53 g for 1.75 mm.
That matters if you are estimating remaining filament by eye on a large-diameter machine: the reel empties visibly faster for the same printed volume.
A note on the filled grades
ABS-CF sits at 1.03 to 1.12 g/cm³ — barely heavier than plain ABS, because chopped carbon fibre is itself a light filler. So the length per kilogram hardly moves, which is unusual among filled filaments. Metal-filled and glass-filled grades behave nothing like this: they add mass without adding much volume, and the same kilogram becomes a much shorter spool.
If you are switching between ABS and ABS-CF, the spool will last about as long. If you are switching between ABS and anything mineral-loaded, it will not.
For a filled grade the number to type into the length and weight converter is the one on its technical data sheet, not the base polymer's, because the filler is several times denser than the plastic carrying it. ABS's stored band, along with everything else about the material, is on the ABS page.