The calculation
meters = net grams ÷ grams per meter
Worked example
At 1.75 mm and an assumed density of 1.24 g/cm³, one meter weighs about 2.983 g. A 100 g remainder is therefore approximately 33.53 m.
Why density must be editable
Material names alone do not determine the density of a particular product. Pigments, blends and fillers can change it. The starting density is a worked-example input, not a universal value for every spool bearing a particular label. Prefer the technical sheet for the exact product.
Where the units go
The filament is modeled as a uniform cylinder. A one-meter length is 1,000 mm long, and one cubic centimeter is 1,000 cubic millimeters. Those factors cancel, so the cross-sectional area in square millimeters times density gives grams per meter directly.
Real filament has diameter variation, and a partly used spool may not have a known tare. Treat the result as a planning estimate. For deciding whether a print will finish, compare measured mass with the slicer estimate and keep a reserve. A long-looking coil is not a reliable substitute for weighing it.
Common questions
Does this measure actual spool length?
No. It is a cylinder-model estimate based on the mass, diameter and density that you provide.
Can I use 2.85 mm filament?
Yes. Enter 2.85 as the diameter and use the density for your specific material.