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What this tool does
Filament looks cheap by the spool and expensive by the print, and most people never connect the two. This filament cost calculator does that connection: enter the spool price, the spool weight, and the weight of one print, and it gives the cost per gram, the filament cost of that print, and how many full prints one spool will make. The result is the filament-only cost, which is the number you need for pricing a print, comparing materials, or deciding whether a cheaper spool is actually cheaper.
The tool runs in your browser and needs no account. It is deliberately simple, because the filament part of a print’s cost is simple arithmetic, and the complications, electricity, failed prints, and your time, are better added afterwards with open eyes than hidden inside a single magic number.
The formula, in plain words
Cost per gram is the spool price divided by the spool weight. A 20 currency-unit spool holding 1,000 grams costs 0.02 per gram. A print weighing 50 grams therefore costs 1.00 in filament. The same spool makes twenty such prints. Nothing else is involved, which is why the tool can be exact about the filament part while being honest that the total cost of a print is higher.
The useful comparison is cost per gram, not cost per spool. A 15-unit spool of 750 grams costs 0.02 per gram, exactly the same as the 20-unit kilogram spool, so neither is a bargain. A 17-unit spool of 1,000 grams costs 0.017 per gram and genuinely is cheaper, even though it costs more than the 750 gram spool. Shoppers who compare spool prices without dividing by weight pay more per print without realising it.
A worked example
Take a practical case: you sell small plant pots that weigh 80 grams each in PLA, and your spool costs 22 for 1,000 grams. Cost per gram is 0.022, so each pot costs 1.76 in filament, and one spool makes twelve full pots, with 40 grams left over. If you price the pot at 8, filament is 22 percent of the price, which leaves room for electricity, packaging, and your time. If you price it at 3, filament alone eats 59 percent, and the print is probably losing money once everything else is counted.
Now change one variable: the same pot in a premium filament at 32 per kilogram. Cost per gram rises to 0.032, each pot costs 2.56, and the spool makes the same twelve pots. The premium material adds 0.80 per pot. Whether that is worth it depends on what the premium buys: better finish, a colour you cannot get otherwise, or a material property the cheap spool lacks. The calculator turns that decision from a feeling into a number.
What the filament cost leaves out
Electricity is the next biggest item, and it varies with print time and local prices: a ten-hour print on a heated bed can cost more in power than in filament. Then come failed prints, which every printer produces, supports and brims that are printed and thrown away, and wear on nozzles and beds. A sensible rule for hobby pricing is to double the filament cost as a first approximation of the real cost, then refine it once you have tracked a few real prints.
Your time is the item people most often forget. Slicing, starting, monitoring, removing supports, and finishing a print can take longer than the print itself for small parts. If you sell prints, decide an hourly rate for that work and add it explicitly. A calculator that pretended to include all of this in one number would be guessing; this one gives you the solid filament figure, and you add the rest honestly.
Tips for cheaper prints
The cheapest lever is usually weight, not spool price. Hollowing a model, dropping infill from 30 percent to 15 percent on a decorative part, or shrinking a part by 10 percent, which cuts weight by about 27 percent, saves more than hunting for a spool that is 2 cheaper. Next, buy the weight you will actually use: a kilogram spool that sits for a year absorbing moisture is worse value than a smaller fresh spool, especially for nylon and PETG.
Finally, weigh your prints. Slicer estimates are good, but they assume perfect extrusion, and real printers over-extrude or under-extrude slightly. Weighing five finished prints and averaging gives a print weight you can trust, and feeding that number back into the calculator makes every later estimate better. This is an educational estimator, and your printer manual and filament maker’s guidance always govern temperatures, materials, and safety.
Related calculators
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- Filament Length Weight Converter – Grams to Metres for PLA, PETG and ABS
- Spool Remaining Filament Calculator – Filament Left from Spool Weight