Filament guide
What did that print cost?
The filament cost of a 3D print is the grams it used times what each gram of that spool cost you. Add the electricity if you want the whole figure. Both are simple sums; the hard part is having the grams and the price to hand for every print.
Cost per gram, then cost per print
Divide what you paid for the spool by the grams of filament on it (not counting the spool):
$20.00 ÷ 1,000 g = $0.02 per gram
37 g print × $0.02 = $0.74 of filament
A multi-color print uses several spools, so price each color's grams at its own spool's price and add them up. A cheap black and an expensive silk in the same print are not the same cost per gram.
Adding the electricity
Energy is the printer's average power draw times how long the print ran: watts × hours ÷ 1,000 gives kilowatt-hours, and your electricity rate turns that into money.
120 W × 3 h ÷ 1,000 = 0.36 kWh
0.36 kWh × $0.17 = $0.06 of power
Use the average draw over a whole print, not the peak while the bed heats. A plug-in power meter gives you the real number for your printer.
Where the grams come from
- The sliced file. Most slicers write the grams per filament into the .gcode or .gcode.3mf they export.
- The printer. Some printers report what a finished job used.
- The scale. Weigh the spool before and after. Slow, but exact.
A print you cancel halfway didn't use the whole job's filament. Count the share it got through.
How Spoolroom adds it up
- Enter what you paid when you add a spool. Each print then shows its Filament, Power and Total cost, with every color priced at its own spool.
- The grams come from the sliced file you drop in, or from a printer that logs its own prints through the Spoolroom watcher. A canceled or failed print takes off only the share it got through.
- Power needs your electricity rate (Settings → Workshop) and each printer's average watts. Until those are set, or while a spool has no price, the cost shows as — or is marked partial, rather than a total that looks cheaper than the print really was.