What a print actually costs
The cost of an FDM print is mostly filament plus a little electricity. The filament share is just the mass used times the per-gram price of the spool: a 100 g print from a 25-per-kilo spool is 100/1000 × 25 = 2.50. The electricity share is the print time times the printer's average power draw times your per-kWh rate: five hours at 120 W is 0.6 kWh, or about 0.09 at a 0.15/kWh rate. Wear on nozzles, belts, and bearings is real but small and hard to pin down, so this calculator leaves it out — add a flat per-print figure if you want to account for it.
Weight or length
Slicers report filament use as both a mass and a length, and this tool converts between them from the material density and filament diameter. A 1 kg spool of 1.75 mm PLA is about 335 metres, so the common rule of thumb "roughly 330 m per kilo" holds for PLA. Denser materials (PETG, polycarbonate) give slightly less length per kilo; the density table the converter uses:
| Material | Density (g/cm³) | 1.75 mm length per kg |
|---|---|---|
| PLA | 1.24 | ~335 m |
| PETG | 1.27 | ~327 m |
| ABS | 1.04 | ~400 m |
| TPU | 1.21 | ~344 m |
| Nylon | 1.14 | ~365 m |
The flow-rate speed limit
Here is the number slicers rarely stop you from exceeding. The plastic a printer lays down per second — the volumetric flow — is layer height × line width × print speed. A 0.2 mm layer, 0.4 mm wide, at 60 mm/s is 0.2 × 0.4 × 60 = 4.8 mm³/s. Every hotend has a maximum rate at which it can melt filament: around 11 mm³/s for a stock brass nozzle, 24 or more for a high-flow hotend. Ask for more flow than that and the extruder physically cannot keep up, so the print under-extrudes no matter what speed the slicer allowed. Rearranged, the flow limit sets a maximum usable speed: 11 mm³/s at that same 0.2 × 0.4 geometry caps you at 137 mm/s. This is why doubling print speed without checking flow — or without a high-flow hotend — produces weak, gappy prints.
Why there is no print-time estimate here
Honest print-time estimation requires simulating the actual toolpath — accelerations, travel moves, cooling waits — which is exactly what your slicer already does when it gives you a time. Any web page that estimates print time from a couple of numbers is guessing, often by ±50%. So this calculator takes grams, length, or hours from your slicer and does the parts it does not: cost and the flow ceiling.
Related tools: the battery life calculator uses the same watt-hour energy math, and the unit converter handles any unit conversions your spool spec throws at you.