Density and price of 3D printing filaments
The density of each material, what a kilo costs and how many metres it gives. The three numbers you need to work your parts out.
Written by Álvaro Melgar Merenciano·
Density decides how many metres a kilo holds, and price per kilo decides what each gram costs you. With those two numbers and the weight of your part you already have the material cost; the rest — power, machine, failures — is what the 3D printing cost calculator adds.
| Material | Density (g/cm³) | Price per kg | Metres per kg (1.75 mm) | Good for |
|---|---|---|---|---|
| PLA | 1.24 | $15 – $25 | 335 m | Decorative parts, prototypes, anything that won't get hot. |
| PLA+ | 1.24 | $18 – $28 | 335 m | Same as PLA but it takes a knock far better. |
| PETG | 1.27 | $18 – $28 | 327 m | Functional parts, outdoors, contact with water. |
| ABS | 1.04 | $18 – $30 | 400 m | Parts that take heat. Needs an enclosure. |
| ASA | 1.07 | $22 – $38 | 389 m | Proper outdoor use: it doesn't yellow in the sun. |
| TPU (flexible) | 1.21 | $25 – $45 | 344 m | Cases, wheels, gaskets, anything that bends. |
| Nylon (PA) | 1.14 | $30 – $60 | 365 m | Gears and rubbing parts. Soaks up moisture. |
| PC (polycarbonate) | 1.20 | $35 – $65 | 346 m | Hard, clear parts that take a beating. |
| Wood / PLA | 1.15 | $25 – $40 | 362 m | Wood-like finish. Wears the nozzle down. |
| Carbon fibre / PETG | 1.30 | $35 – $60 | 320 m | High stiffness. Needs a hardened steel nozzle. |
The prices are brackets, not a price list
Filament prices move a lot: between brands, between colours from the same maker, between a Black Friday deal and a one-off purchase. The ranges in the table are ballpark figures for a normal purchase. A supermarket-brand PLA on offer can drop below $15/kg and a premium PLA with a special finish passes $30/kg without blinking. Use the bracket to get your bearings and always type what your spool actually cost you into the calculator.
The same kilo does not give the same metres
Comparing materials by the price of a kilo is the usual thing to do, and it is incomplete. A kilo of ABS brings 400 metres and a kilo of PETG 327, so for the same money you take home a lot more thread in one than in the other.
Dividing the middle of each bracket by the metres a kilo gives produces another table, and that one really compares:
| Material | Average price | Metres per kg | Cents per metre | Per cm³ |
|---|---|---|---|---|
| PLA | $20 | 335 m | 6.0 | $0.025 |
| ABS | $24 | 400 m | 6.0 | $0.025 |
| PLA+ | $23 | 335 m | 6.9 | $0.029 |
| PETG | $23 | 327 m | 7.0 | $0.029 |
| ASA | $30 | 389 m | 7.7 | $0.032 |
| Wood / PLA | $32.50 | 362 m | 9.0 | $0.037 |
| TPU | $35 | 344 m | 10.2 | $0.042 |
| Nylon | $45 | 365 m | 12.3 | $0.051 |
| PC | $50 | 346 m | 14.4 | $0.060 |
| Carbon fibre / PETG | $47.50 | 320 m | 14.9 | $0.062 |
The first line is the surprise: PLA and ABS cost the same per metre, six cents, even though a kilo of ABS is 20% dearer. What ABS loses on price it wins back on density, because weighing less per cubic centimetre means a kilo of it gives 65 metres more.
And the last column puts the real scale in place: between the cheapest plastic and the dearest there is a factor of two and a half, not ten. However expensive a technical material sounds, a cubic centimetre of polycarbonate is six cents.
Why density matters more than it looks
Picture the same part printed in ABS (1.04 g/cm³) and in PETG (1.27 g/cm³). The same volume of plastic weighs 22% more in PETG, so you spend 22% more grams and the material costs you 22% more, even if both kilos cost the same. The other way round: a kilo of ABS gives you about 400 metres and a kilo of PETG about 327. If you buy by the kilo and plan by the metre — or the other way round — that gap lands straight in your price.
Denser is not stronger
This is the most common misunderstanding about this table, and the table itself disproves it. Density says how much a cubic centimetre weighs, and nothing else. It says nothing about impact resistance, about heat, or about whether it snaps.
Three examples from the list above, which are worth the whole explanation:
- PETG (1.27) is denser than polycarbonate (1.20) and than nylon (1.14), and both of those run rings around it mechanically.
- TPU (1.21), the softest of the lot, weighs more per cubic centimetre than polycarbonate, which is among the hardest.
- ABS (1.04) is the lightest in the table and takes heat far better than PLA (1.24), which is among the heaviest.
So density is for what density is for: turning volume into grams and grams into metres. Choosing a material looks at other properties, and the most practical of them is usually the temperature at which the part starts to soften.
The one thing a high density does tell you is that the same part will cost you more in grams, and that alone is reason enough to keep the number handy.
How to check the density of your own filament
The table holds catalogue values. If you want the one for your particular spool, there is a test that takes an hour and costs ten cents: print a 20 mm calibration cube at 100% infill, dry it, weigh it on a kitchen scale and divide.
A 20 mm cube is exactly 8 cubic centimetres, so the sum is direct: grams divided by eight, and that is your density in g/cm³. This is what the scale should read:
| Material | Density | Cube weight |
|---|---|---|
| ABS | 1.04 | 8.32 g |
| ASA | 1.07 | 8.56 g |
| Nylon | 1.14 | 9.12 g |
| Wood / PLA | 1.15 | 9.20 g |
| PC | 1.20 | 9.60 g |
| TPU | 1.21 | 9.68 g |
| PLA and PLA+ | 1.24 | 9.92 g |
| PETG | 1.27 | 10.16 g |
| Carbon fibre / PETG | 1.30 | 10.40 g |
If your PLA cube weighs 9.9 grams, the table's density works for you and you can trust the rest of the numbers. If it weighs 9.4, there is half a gram missing, and it is hardly ever the density's fault: it is usually under-extrusion, meaning your machine lays down less plastic than it thinks. That is fixable by calibrating the flow, and it improves the strength of everything you print along the way.
And if it weighs more than it should, there is flow to spare. Either way the cube test has told you something useful, even if it was not what you were looking for.
What happens if you leave the density wrong
It is worth knowing where this number enters and where it does not, because hardly anybody is clear on it.
It does not enter the cost of a part once you know what it weighs. If the slicer tells you 60 grams and your spool cost $20 a kilo, the material is $1.20 and density plays no part.
It does enter in three places, and in all three it shows:
- In the metres per kilo. Leaving PLA's 1.24 in place for a spool of ABS tells you 335 metres when there are really 400: the reel holds 19% more filament than you think.
- In the weight your slicer predicts, which comes from the part's volume multiplied by the density. If that is wrong, the grams are wrong, and then so is the cost.
- In any conversion between grams and metres, which is exactly what the grams to metres converter does.
The practical rule: if you take the grams from the slicer, make sure the material profile you have loaded is the plastic you are actually using, and not the PLA one that came from the factory.
The spools that are not one kilo
There is a trap that has nothing to do with density and wrecks any price comparison: not every spool holds a kilo. 750 gram spools are common, and 500 or 800 gram ones turn up too, especially in technical materials and special colours.
A 750 gram spool at $18 is not $18 a kilo: it is $24 a kilo. And an 800 gram one at $20 is $25. Set against an ordinary PLA at $20 a kilo, what looked cheaper is 20% dearer.
The sum is one you can do in your head: price divided by the real kilos. And the same goes for the calculator: in the spool weight field type the grams yours actually holds, not 1,000 out of habit.
Watch the advertised weight too: the one that counts is the plastic, not the whole thing with the reel, which can weigh 200 grams on its own.
Which one to pick, in one line each
- PLA: easy, cheap and enough for nearly anything decorative. Warps in a car in the sun.
- PLA+: same cost to print with far less brittleness.
- PETG: the natural step up for functional parts, outdoors and water contact.
- ABS and ASA: heat and sun resistant, but they want an enclosure and ventilation.
- TPU: flexible; prints slowly and not every machine feeds it well.
- Nylon and PC: serious mechanics, high temperatures and compulsory drying.
- Filled ones (wood, carbon fibre): finish or stiffness in exchange for nozzle wear; with carbon fibre, a hardened steel nozzle is not optional.
Careful with the density of filled filaments
A «wood PLA» isn't PLA: it carries fibre particles that change its density, and the same goes for carbon-filled, metal-filled or foaming filaments (LW-PLA), whose effective density drops enormously when printed because the material expands. In those cases the number in the table is an approximation: check what the manufacturer says and type it into the density field by hand.
The foaming ones are the extreme case and deserve their own warning: their density depends on the temperature you print at, because more heat means more foaming and a fatter strand. With those, no table gets it right and the cube test is the only reliable answer — and it has to be repeated if you change the temperature.
Where you change that number
Density is not something you touch on the printer: it lives in your slicer's filament profile, next to the temperatures and the diameter. It is almost always called «density» and goes in g/cm³.
Next to it there is usually another field for the price per kilo, and it is worth filling in: it is what makes the slicer tell you outright what the material of each print costs, without you having to multiply anything.
Two warnings that save grief. First: duplicating a profile for a new material drags the old density and price along with it, and that is where half of all strange calculations are born. Second: the diameter lives in that same place, and if your spool is 2.85 mm and the profile says 1.75, your problem is not the cost — the print is going to come out wrong.
The same applies here: the density field in these tools is editable on purpose. It fills itself in when you pick a material from the list, but you can type your datasheet's number over it.
How much the final cost changes by material
Less than people fear. On a 60 gram part that takes five hours, moving from PLA at $20/kg to PETG at $24/kg puts the total cost up about 25 cents, because material is only part of the total. Moving to nylon at $45/kg puts it up around $1.65. Check it with your own numbers in the calculator, which has a button to compare two materials side by side, or look at the costs of 20 typical parts.
If what you want is the breakdown material by material, with what the same part costs in each and what it adds up to over a whole year, that is in what it costs to print in PETG, ABS or TPU.
Want the exact number for your own case? 3D printing cost calculator does the full sum with your filament, your electricity tariff and your printer, and leaves the quote ready to copy.
Frequently asked questions
What is the density of PLA?
1.24 g/cm³ for standard PLA, and the same value for PLA+.
At that density, a kilo of 1.75 mm PLA gives about 335 metres of filament.
How much does a kilo of filament cost?
A normal-grade PLA runs between $15 and $25 a kilo, and PETG between $18 and $28.
Technical materials climb steeply: nylon runs $30 to $60 and polycarbonate can pass $65.
Which is stronger, PLA or PETG?
PETG takes impacts, heat and humidity far better; PLA is stiffer but more brittle and softens from about 55-60 °C.
For functional or outdoor parts, PETG; for figures and decoration, PLA.
Why does ABS give more metres per kilo?
Because it is less dense: 1.04 g/cm³ against PLA's 1.24.
The same kilo takes up more volume and therefore more length of strand: about 400 metres against 335.
Does density affect the weight of the printed part?
Yes, directly. The same part at the same infill weighs more in PETG than in ABS.
Since filament is sold by weight, that changes the material cost even if the price per kilo is identical.
How do I find the real density of my spool?
Print a 20 mm calibration cube at 100% infill and weigh it: it is exactly 8 cubic centimetres, so the grams divided by eight are your density.
A PLA cube should weigh 9.92 g and an ABS one 8.32 g. If yours weighs a good deal less, the likely culprit is not the density but your machine under-extruding.
Do I compare filaments by the price per kilo or per metre?
By the kilo if you are going to work in grams, which is the normal case, because the slicer gives you grams. By the metre only if you are measuring what is left on the reel.
The two do not say the same thing: PLA and ABS both cost 6 cents a metre, even though a kilo of ABS is 20% dearer, because being less dense it gives 65 metres more per kilo.
What density do I use if my filament isn't listed?
Check the manufacturer's data sheet: density is usually quoted in g/cm³.
The density field in the tools is editable for exactly that reason; if you can't find the figure, 1.24 is a reasonable approximation for any PLA variant.
More tools and guides
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