3D printing cost per gram: the math, an example and a table
The cost-per-gram formula
It is a single division:
cost per gram = total paid for the spool ÷ net filament weight, in grams
Two details get the math right:
- Use what you actually paid. If the spool cost $17 and shipping was $3, the spool cost $20. If it came in a four-pack, divide the order total by four. Coupons count too: what matters is what left your pocket.
- Use the net weight, without the spool. The label weight is the filament. Not every spool is 1 kg: there are 250 g, 500 g, 750 g and 3 kg spools, and the divisor changes with them. If you weigh the spool on a scale, subtract the empty spool. Empty spool weight varies from brand to brand, so weigh an empty one of the same brand once and write it down.
Ready table: cost per gram by spool price
Find what you paid for a 1 kg spool and read the cost per gram and the cost of an 85 g print.
| 1 kg spool price | Cost per gram | 85 g print |
|---|---|---|
| $14 | $0.014 | $1.19 |
| $16 | $0.016 | $1.36 |
| $20 | $0.020 | $1.70 |
| $24 | $0.024 | $2.04 |
| $30 | $0.030 | $2.55 |
Math examples, not store quotes: 1 kg net spool and 85 g of total consumption.
For other spool sizes, divide by their weight. A 500 g spool for $12 works out to $0.024 per gram; a 750 g spool for $16.50 to $0.022.
Step-by-step example
Imagine a headset stand whose total weight estimated by Bambu Studio is 85 g of PLA, supports included. The spool cost $20 with shipping.
- Cost per gram: $20 ÷ 1,000 g = $0.02/g.
- Material for the print: 85 g × $0.02 = $1.70.
- Losses the slicer did not count: if the 85 g is all the filament in the estimate, material costs $1.70. If you know of another 5% that is not in the estimate, it goes to $1.79.
Run the numbers on your spool
Material for the part
Cost per gram
Calculated in your browser, with the same formulas as the calculator.
Bambu Studio, OrcaSlicer, PrusaSlicer and Cura show grams in the summary after slicing. Use the total weight: it already adds up the model, supports, brim, prime tower and the color-change purge when there is one. Adding a purge percentage on top of that total counts the same filament twice.
When the slicer shows meters instead of grams
The weight of one meter depends on the diameter and the density of the material. For 1.75 mm filament:
| Material | Density used | Grams per meter |
|---|---|---|
| PLA | 1.24 g/cm³ | about 2.98 g |
| PETG | 1.27 g/cm³ | about 3.05 g |
| ABS | 1.04 g/cm³ | about 2.50 g |
| TPU | 1.21 g/cm³ | about 2.91 g |
Approximate values. Density varies by manufacturer and formulation: check yours in the slicer's material profile or on the spool's data sheet.
The same part weighs less in ABS
For the same volume of plastic, ABS weighs less than PLA because it is less dense. Using 1.04 g/cm³ for ABS and 1.24 g/cm³ for PLA, 85 g of PLA is equivalent to about 71.3 g of ABS. If both spools cost the same per kilo, the part is cheaper in ABS.
That only shows up in the estimate if the slicer's filament profile is set to the right material. With a PLA profile loaded, it calculates the weight with PLA's density.
What the cost per gram leaves out
The cost per gram is exact. What can be missing from the math is filament that never becomes a part and is not in the estimate:
- Failed prints. A part lost halfway uses material without becoming a sale. How much to set aside depends on your own failure rate: see the guide to failure rate pricing.
- The end of the spool. When what is left is not enough for a whole part, it becomes waste. How much depends on your parts.
- Wet filament. A spool that has absorbed moisture can print badly. Storing it well avoids losing material.
- Color changes. The swap purge is already in the slicer total, but it can weigh more than the part itself. The guide to multicolor waste cost shows how to cut it.
From cost per gram to the price of the part
Material is only one part of the cost. Charging just twice the material can leave electricity, printer wear, labor and selling fees uncovered. Work out the full cost before you set your margin: the guides to 3D printer cost per hour and how much to charge for 3D printing show how.
Frequently asked questions
Does the weight of the spool count?
No. The label weight is the filament. If you weigh the whole spool to see how much is left, subtract the empty spool, which varies from brand to brand: weigh an empty one of the same brand once and note it down.
Is a 3 kg spool or a multi-pack cheaper per gram?
It depends on the deal: do the same math, total price divided by total weight. And it only pays off if you use it all before the filament picks up moisture, or if you can store it sealed with desiccant.
How do I know how many grams a part will use before printing?
Slice it and check the slicer summary: it shows the total weight with supports, brim and purge. In the MakerPrice 3D calculator you can import the G-code or the sliced 3MF, and the weight and time fill in by themselves.
How many parts can I make from 1 kg of PLA?
Divide 1,000 g by the weight of each print. In theory, a 1 kg spool makes 11 parts of 85 g or 83 keychains of 12 g. If each keychain uses 5% more than the estimate, that is 79.
Does imported or premium filament change the math?
The math is the same; only the total price changes. Add shipping and any import duty to what you paid before dividing by the weight.