Convert filament between length and weight in either direction. Useful for estimating how much spool you have left, planning a print against remaining filament, or sanity-checking a slicer’s usage estimate.
How it works
Filament is a solid cylinder, so its weight follows directly from geometry and density.
area (cm²) = π × r² (r = diameter ÷ 2, in cm)
mass per meter (g/m) = area × 100 cm × density
For 1.75mm PLA: the radius is 0.0875 cm, so area = π × 0.0875² ≈ 0.02405 cm². At a
density of 1.24 g/cm³, each meter (100 cm) weighs 0.02405 × 100 × 1.24 ≈ 2.98 g.
From there:
- Length → Weight: weight = length (m) × mass per meter
- Weight → Length: length = weight (g) ÷ mass per meter
Why diameter dominates
Because area depends on r², weight scales with the square of the diameter. A 2.85mm strand has
about (2.85 ÷ 1.75)² ≈ 2.65× the cross-section of a 1.75mm strand, so the same length weighs
roughly 2.65 times as much. Always pick the correct diameter or the result can be off by more
than half.
Example: how much is left on a spool
You weigh a partly-used PLA spool at 540g. The empty spool weighs 210g, so 330g of filament
remains. Using Weight → Length for 1.75mm PLA (2.98 g/m), that is about 330 ÷ 2.98 ≈ 110 m
left — enough to plan your next few prints. Everything is computed locally in your browser.