Formula
Material is grams times the spool price divided by the grams on the spool. Electricity is watts divided by 1000, times hours, times the price of a kilowatt-hour. The machine line is your hourly rate times hours. Markup is a percent on that sum.
cost = material + electricity + machine
price = cost × (1 + markup)
If grams come from length, the volume is the cylinder of the filament. A 1.75 mm diameter and 100 m of PLA at 1.24 g/cm³ is about 298 g. Densities are typical, and the spool label wins. The machine rate defaults to $0.50 an hour and is not a model of depreciation. The price is what you would type into the Etsy fee calculator, the PayPal fee calculator, or the Stripe fee calculator.
Worked examples
200 g, spool $20 per 1,000 g, 200 W for 8 hours at $0.15/kWh, machine $0.50/h, 50% markup. Filament $4.00. Power $0.24. Machine $4.00. Cost $8.24. Price $12.36.
100 m of 1.75 mm PLA at 1.24 g/cm³. The cylinder is about 298 g. The rest of the cost uses whatever spool, power, and hours you still have filled in.
Reference
Typical densities. Replace them when the spool says otherwise.
| Plastic | g/cm³ |
|---|---|
| PLA | 1.24 |
| PETG | 1.27 |
| ABS | 1.04 |
Questions
Where does the gram weight come from?
From the slicer, if you type it. Or from length × the filament’s cross-section × density, if you turn on the length path. PLA at 1.24 g/cm³, PETG at 1.27, and ABS at 1.04 are typical. The spool label wins.
What is the machine rate?
A number you choose, defaulting to $0.50 an hour. It is not a depreciation model. Put in whatever you actually want to recover for the printer, the nozzle, and the failed prints you do not itemize.
How do I turn the price into a fee?
The price after markup is the sale. The Etsy, PayPal, and Stripe calculators take that sale and subtract their fees. This page does not know those rates.
Sources
- Filament mass = length × π × radius² × density. PLA 1.24, PETG 1.27, and ABS 1.04 g/cm³ are typical values, not a resin datasheet.
- Electricity is average watts × hours ÷ 1,000 × your rate. The $0.50 per hour machine rate is a default for this page.