How long is a spool of filament?
Spools are sold by mass, not by length, so determining exact length of each spool is not possible. However, we can estimate how long a spool of filament is based on the type and its diameter.
Here's a chart of common filaments and their densities:
| Filament Type | Density (g/cm^3) |
| PLA | 1.24 |
| ABS | 1.03 |
| PET/PETG/PET+/ColorFabb XT | 1.27 |
| TPU | 1.20 |
| Flexible PLA | 1.26 |
| ColorFabb nGen | 1.20 |
| TPE (e.g. NinjaFlex, SemiFlex) | 1.20 |
| bronzeFill, copperFill, brassFill, steelFill | 3.90 |
| woodFill | 1.15 |
| GMASS Tungsten Metal ABS | 4.00 |
| Nylon | 1.15 |
| NylonX | 1.00 |
| Ryno | 1.27 |
Once we have the density, we need the mass of the spool and the diameter of the filament. For this example we have a 1 kg spool of ABS that is 1.75 mm in diameter.
Here's the formula:
Length (m) = ( Mass (g) / Density (g/cm3) ) / ( π (3.14159) * (Diameter (mm) / 2)2 )
So for our example, the equation would be:
Length (m) = ( 1000 / 1.04 ) / ( π (3.14159) * (1.75 / 2) 2 )
Length (m) ~= 400
Length (ft) = Length (m) * 3.28084, so
Length (ft) = 1312