Between 1.5 and 2.8 cents a gram. That is simply the $15 to $28 a kilogram PLA sells for at mainstream retail, divided by a thousand.
The conversion is trivial. The interesting part is what a gram of PLA actually is, and which of the three ways of quoting the price you should be using.
Three units, one spool
At a mid-range $22 a kilogram:
- Per gram: 2.2 cents. Useful for costing a part, because the slicer reports mass.
- Per metre: about 6.6 cents. One metre of 1.75 mm PLA weighs 2.98 g. Useful when you are estimating from filament left on the reel rather than from a slicer.
- Per cubic centimetre: about 2.7 cents. PLA at 1.24 g/cm³ puts 806 cm³ in a kilogram. This is the unit to use when comparing materials, because it prices the volume of part you get rather than the mass of plastic.
Why the per-gram price flatters cheap filament
A gram is a gram, but a gram of one PLA does not fill the same space as a gram of another. Matte PLA loaded with mineral filler runs up to 1.35 g/cm³ against plain PLA's 1.24, so the same printed object comes out heavier and the same spool holds 307.96 m instead of 335.28 m — 8.1% less filament for the same money.
Two spools at an identical price per gram can therefore differ by nearly a tenth in what they will actually build. Comparing per cubic centimetre removes that entirely.
The number to use when quoting work
Not this one. Filament is usually the smallest of the four terms in a print's cost — on an eight-hour job it is routinely outweighed by machine time alone — so a quote built from cents per gram is a quote missing most of its cost.
Cost per gram is the right unit for one thing: deciding whether a spool is good value against another spool. For anything downstream of that, the mass has to be joined by hours.
To move between grams, metres and cubic centimetres for your own spool, use the length and weight converter. To see how small a share of a real job the plastic is, put a part through the print cost calculator.