The formula
cross-section = π × (diameter ÷ 2)²
One metre of filament is a long cylinder whose volume in cm³ equals its cross-section in mm² (because 1 mm² × 1,000 mm = 1 cm³). 1.75 mm filament has a cross-section of 2.405 mm², so a metre is 2.405 cm³ — about 2.98 g of PLA at 1.24 g/cm³.
Metres per kilogram
| Material | Density | 1.75 mm: m per kg | 1.75 mm: g per m | 2.85 mm: m per kg |
|---|---|---|---|---|
| PLA | 1.24 g/cm³ | 335 m | 2.98 g | 126 m |
| PETG | 1.27 g/cm³ | 327 m | 3.05 g | 123 m |
| ABS | 1.04 g/cm³ | 400 m | 2.50 g | 151 m |
| ASA | 1.07 g/cm³ | 389 m | 2.57 g | 146 m |
| TPU | 1.22 g/cm³ | 341 m | 2.93 g | 128 m |
| Nylon | 1.12 g/cm³ | 371 m | 2.69 g | 140 m |
| PC | 1.22 g/cm³ | 341 m | 2.93 g | 128 m |
Densities from Prusament technical data sheets (PLA, PETG, ASA, PC Blend), Bambu Lab (TPU 95A HF) and Polymaker (PolyMide CoPA nylon); the ABS figure is the commonly quoted generic value. Brands and blends differ — fillers such as carbon fibre, wood or metal change the density, so use the figure on your spool’s data sheet when you have it.
How much filament is left on my spool?
- Weigh the spool on a kitchen scale.
- Subtract the empty spool. Many brands print it on the label or list it online; plastic spools are often 150–250 g, cardboard spools less. Weigh your first empty spool of each brand and note it.
- Convert the rest to metres with the calculator and compare with the length your slicer says the print needs, plus a few metres to spare.
Tolerance matters. Filament diameter tolerance (often ±0.02 mm) changes the weight per metre by about 2.3% either way at 1.75 mm (1.4% at 2.85 mm) — another reason to leave a margin before starting a long print.
Last reviewed: 2026-10-04 · Disclaimer