3D print cost calculator: filament, electricity and failed prints

What goes into the number

The calculator adds four things:

1. Filament. Grams used × price per gram, where price per gram = spool price ÷ net grams on the spool. Use the net filament weight printed on the label, not the gross weight with the spool.
2. Waste allowance. An optional percentage added to the filament only. It covers material you pay for but do not keep: purge and prime towers, brims and supports you throw away, and a share of failed prints.
3. Electricity. Energy in kWh = average watts × hours ÷ 1000, then × your tariff.
4. Other. A fixed amount per print for anything else you want to count, such as glue stick, a replacement nozzle spread over many prints, or packaging.

Everything is in whatever currency you enter; the calculator does not convert currencies.

Getting the inputs right

Grams used. Take it from the slicer’s print estimate after slicing the full plate. If your slicer shows only length, convert it with the length and weight calculator using the density from the filament’s data sheet.

Average power. This is the input people most often get wrong. The number on the power supply is a ceiling, not the average draw. Heaters run at full power while warming up and then cycle on and off to hold temperature, so the average over a print is much lower. Prusa measured an average of 80 W for an MK-series printer printing generic PLA and 120 W printing generic ABS, at a room temperature of 26 °C ^[1]. The difference between the two comes mostly from the higher bed and nozzle temperatures ABS needs. A plug-in energy meter between the wall and the printer is the most reliable way to find your own value: run a typical print and divide the kWh it reports by the hours.

Tariff. Use the price per kWh on your electricity bill, including any per-kWh taxes and fees.

Worked example

A 120 g PLA print on a spool that cost 20 for 1,000 g, taking 5 h 30 min on a printer averaging 80 W, at 0.17 per kWh:

The electricity share here is under 3% of the total. It grows with long, light prints on high-temperature materials, and with enclosed printers that heat a chamber.

What the calculator leaves out

Printer depreciation, maintenance parts and your time are real costs but depend on how you account for them. If you sell prints, add them through the “Other cost per print” field or as a margin on the result. Prusa’s FAQ, for example, puts the average maintenance interval of its printers at around 800 print hours, most often for a nozzle change ^[1]; dividing a part’s price by such an interval is one way to spread maintenance cost across prints.

The waste allowance is deliberately simple. If one print in ten fails halfway, a 5% allowance is a reasonable first guess; if you print multi-color jobs with a purge tower, the slicer’s purge estimate is better included in grams used directly.