3D Printer Filament Length Calculator (Metres From Grams)
Length of filament in a spool from its weight, material and diameter, plus the weight and cost of each metre.
Results
Length of filament
335.3
m
Weight of one metre
2.983
g/m
Cost per metre
0.066
Cost of that much filament
22.00
What this tool does
A filament is a thin cylinder of plastic, so its length is the mass divided by the density times the cross-section area. A metre of 1.75 mm PLA weighs about 3 g, which is why a 1 kg spool holds roughly 330 m; 2.85 mm filament (often called 3 mm) has about 2.7 times the area, so the same kilogram is only around 125 m. Densities are typical values, PLA about 1.24, PETG about 1.27 and ABS about 1.04 g/cm³, and brands with additives or fillers differ. Use the net weight of the filament, not the spool with its reel.
Formula
length = mass ÷ (ρ × π × (d ÷ 2)²) · grams per metre = ρ [g/cm³] × π (d/2)² [mm²]
Variables
| Symbol | Meaning | Unit |
|---|---|---|
m | Mass of filament | g |
mt | Material | — |
ro | Density if you chose Other | g/cm³ |
d | Filament diameter | mm |
pk | Price per kilogram of filament | — |
L | Length of filament | m |
GM | Weight of one metre | g/m |
CM | Cost per metre | — |
CT | Cost of that much filament | — |
Worked example
- Mass of filament1000 g
- Material1
- Density if you chose Other1.24 g/cm³
- Filament diameter1.75 mm
- Price per kilogram of filament22
- Length of filament335.3 m
- Weight of one metre2.983 g/m
- Cost per metre0.066
- Cost of that much filament22.00
Limitations
- Density changes with temperature, moisture and composition. Use a value from the supplier's data sheet whenever precision matters.
- The default values are typical reference figures, not measurements of your situation. Replace them with your own data whenever you have it.