3D Printer Filament Spool Length Calculator
Convert filament weight to length in meters and feet.
Supports PLA, PETG, ABS, ASA, and TPU at both 1.75 mm and 2.85 mm diameters.
How filament length is calculated
Filament is sold by weight (typically 1 kg spools), but slicers often report usage in meters or grams. Knowing how much length remains on a partial spool helps you plan prints and avoid running out mid-job.
The formula
The cross-section of a filament strand is a circle with area = π × (d/2)². Multiplied by the length and the material density, this gives the total mass. Rearranging to solve for length:
Length (mm) = Mass (g) / (π × (diameter/2)² × density)
Where:
- Mass is the weight of filament only (subtract spool weight if weighing the full spool)
- Diameter is the filament diameter (1.75 mm or 2.85 mm)
- Density varies by material (see below)
Material densities used in this calculator
| Material | Density (g/cm³) |
|---|---|
| PLA | 1.24 |
| PETG | 1.27 |
| ABS | 1.05 |
| ASA | 1.07 |
| TPU (95A) | 1.21 |
Practical tip: tare your scale
Most empty spools weigh 200–250 g for 1 kg spools. Place the full spool on a kitchen scale, note the total weight, then subtract the known empty spool weight to get the filament-only mass. Many manufacturers print the spool weight on the label or packaging.
Standard spool lengths for reference
A full 1 kg spool of 1.75 mm PLA contains approximately 330 meters (1,080 feet). A full 1 kg spool of 2.85 mm PLA contains approximately 125 meters (410 feet). PETG and TPU spools are slightly shorter due to higher density.