Filament Cost Calculator: Grams from Spool Length
Turn the length on a spool label into grams, then into the cost of the filament your print uses. Enter the diameter, the density and the spool price.
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This is not a slicer. Take the grams or the length and the print time from your slicer, then enter the rest here.
Density presets, g/cm³. Each one names its source below. Use the value on your spool label when it has one:
Sources: PLA, Prusament PLA safety data sheet, section 9.1. PETG, Prusament PETG technical datasheet, typical material properties. ABS, Wikipedia, Acrylonitrile butadiene styrene, median density 1.07 g/cm³. TPU 95A, Prusament TPU 95A technical datasheet, typical material properties.
| Part of the cost | Per print |
|---|
Cost per print = (filament + electricity + wear + labour) ÷ (1 − failure rate). Price for selling = cost per print ÷ (1 − profit margin).
How to work out the cost of a spool of filament
- Choose length and diameter. Enter the length in metres and the diameter in millimetres, as printed on the spool label.
- Choose PLA, PETG, ABS or TPU to fill in the density, or type the density from your spool sheet.
- Enter the spool price and the spool weight. The page turns the length into grams and prices those grams.
- Read the grams and the filament cost. Choose grams instead if your slicer already gives the weight.
A 40 m spool, worked out by hand
Take the first row of the table. A 1.75 mm rod has a radius of 0.875 mm, or 0.0875 cm. Its cross section is π × 0.0875², which is 0.0241 cm². A 40 m length is 4000 cm, so the volume is 96.2 cm³. At 1.24 g/cm³ that weighs 119.3 g, which the page shows as 119 g.
At 25 EUR for a 1000 g spool, those grams cost 2.98 EUR. This is a calculation, not a weighed spool, and the other two rows of the table come from the same formula.
Three spools, three prices
| Spool | Grams | Filament cost |
|---|---|---|
| 40 m, 1.75 mm, PLA 1.24 g/cm³, 25 EUR per 1000 g | 119 g | 2.98 EUR |
| 100 m, 1.75 mm, PETG 1.27 g/cm³, 20 EUR per 1000 g | 305 g | 6.11 EUR |
| 40 m, 2.85 mm, PLA 1.24 g/cm³, 20 EUR per 1000 g | 316 g | 6.33 EUR |
The diameter matters more than the length here. The 2.85 mm rod has about 2.65 times the cross section of the 1.75 mm rod, so the same 40 m weighs 316 g instead of 119 g.
Where the density figure comes from
The density buttons fill in 1.24 g/cm³ for PLA, 1.27 for PETG, 1.07 for ABS and 1.25 for TPU 95A. The PLA, PETG and TPU values are in Prusament sheets by Prusa Polymers, and the ABS value is the median in the Wikipedia article on ABS. The page names each source under the buttons. These are reference values, not measurements of your spool. Another brand can be a little denser or lighter, so the number on your spool sheet is the better choice when you have it.
A small change in density changes the grams in the same proportion. A density 2% higher gives 2% more grams, and a 2% higher cost.
Price per kilogram, weight per spool
Spools are sold by their net weight, so a 1000 g spool at 25 EUR costs 0.025 EUR a gram. If the spool you bought holds 750 g of filament, enter 750 for the spool weight. Entering 1000 would make each gram look cheaper than you paid.
The page prices the grams it works out, so the filament cost of one print is those grams times the cost per gram. Electricity, wear and labour are not part of this figure, and the full cost of a print comes from the main calculator.
Checks on the spool label
- Read the diameter from the label, not from the printer setting. 1.75 mm and 2.85 mm are the two common sizes.
- Enter the net weight of the filament, not the weight of the spool with its cardboard core.
- Enter what this spool cost you, not the price of the last one; the cost per gram follows it.
- Take the grams from the slicer when you have them, since they already include supports and a purge line.
Privacy
The content you enter never leaves your device. The page keeps the values in this browser so they are still there on your next visit, and no request carries them.
Frequently asked questions
How do I turn filament length into grams?
Multiply the length by the cross section of the rod and by the density. A 1.75 mm rod has a cross section of about 0.024 cm², so 4000 cm of PLA at 1.24 g/cm³ weighs about 119 g.
Why does the filament diameter change the weight so much?
The cross section grows with the square of the diameter. Filament at 2.85 mm has about 2.65 times the area of 1.75 mm, so the same length weighs about 2.65 times as much and costs about 2.65 times as much.
Does every colour of the same material cost the same per gram?
Often it does not. Brands and colours sell at different prices, and some special finishes cost more. Enter the price of the spool you actually bought, so the grams cost what you paid.
What if my slicer shows the length instead of the weight?
Switch to length and diameter and type the metres from the label. The grams appear first and the cost after them, and the result holds only if the density matches your material.
Does the filament cost include shipping or the spool itself?
No. The cost is the grams you use, priced from the spool price you enter. Shipping, tax and any deposit on the spool are not in the calculation, so add them to the spool price if you pay for them.
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