Filament Length to Weight Calculator
Filament is sold by weight (kg) but slicer software sometimes reports usage in meters. This calculator converts a given length of filament into grams using the material density and filament diameter. The cross-sectional area of the filament (a circle) times the length gives the volume; multiplying by density yields the mass. This is useful for estimating remaining filament, cross-referencing slicer output, and calculating cost from length data.
Filament length to weight formula
Volume (cm3) = pi * (d/20)^2 * L * 100
Weight (g) = Volume * Density (g/cm3)
Where d is diameter in mm and L is length in metres. Converting to cm: radius = d/2 mm = d/20 cm; length in cm = L * 100. Then mass = pi * r^2 * length_cm * density.
Common filament densities
- PLA: 1.24 g/cm3
- PETG: 1.27 g/cm3
- ABS: 1.05 g/cm3
- ASA: 1.07 g/cm3
- TPU (95A): 1.21 g/cm3
- Nylon (PA12): 1.02 g/cm3
- PC (Polycarbonate): 1.20 g/cm3
Filament length to weight calculator: frequently asked questions
What density should I use for PLA?
Standard PLA has a density of approximately 1.24 g/cm3. Filled or modified PLAs (wood-fill, metal-fill) have higher densities, often 1.3 to 1.5 g/cm3. Check the manufacturer datasheet for exact values.
What is the standard filament diameter?
The two standard diameters are 1.75 mm (most common for desktop FDM printers) and 2.85 mm (used by some Ultimaker and older Bowden-drive systems). Measure your spool label or the filament itself to confirm.
Why does weight matter when I know the length?
Slicer software and filament pricing both use weight (grams). Converting length to grams lets you cross-reference slicer estimates, calculate costs, and determine remaining filament on a partial spool.
How do I estimate remaining filament on a partial spool?
Weigh the partial spool, subtract the known empty spool weight, then use this calculator in reverse: weight / (pi * (d/2)^2 * density) = length. Alternatively enter the known remaining length to get grams.
Does filament diameter variation affect the calculation?
Yes. A 1.75 mm nominal filament with actual diameter of 1.77 mm has about 2.3% more cross-sectional area and therefore more mass per metre. Premium filaments hold tighter tolerances (plus or minus 0.02 mm).
Official sources
- NIST: Measurement Needs for Additive Manufacturing.
- ASTM International: ASTM F2792 Standard Terminology for Additive Manufacturing.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.