How to calculate 3D printing cost properly
Almost every "3D print cost calculator" online multiplies grams by price per kilo and calls it a day. That number is real, but it is usually less than a quarter of what the print costs you. Here is the full formula this tool runs:
Filament + Electricity + Machine wear + Labour + Failure buffer = True cost
True cost × (1 + margin) = Sell price
Sell price − platform fees − true cost = What you keep
1. Filament
Weight × price per kg. The calculator gets weight from your actual STL: it computes the exact solid volume of the mesh, then models the shell (walls plus top and bottom skins) and the infill inside it, adds supports if you selected them, and multiplies by the filament's density. A 50 g print at $20/kg is $1.00.
2. Electricity
Watts × hours ÷ 1000 × your rate. A 120 W printer running four hours at $0.16/kWh costs about $0.08. Tiny per print — but across a thousand prints a year it is real money, and it belongs in the number.
3. Machine wear (depreciation)
Every hour of printing consumes nozzle life, belts, bearings and fans. Divide the machine price by a realistic lifetime in hours to get a cost per hour: a $699 printer over 6,000 hours is about $0.12/hour. Charging this is how you fund the replacement instead of being surprised by it.
4. Labour
Slicing, bed prep, removal, support cleanup, packing. Ten minutes at $15/hour is $2.50 — often the single biggest line on a small print. If you are not paying yourself, you do not have a business, you have a hobby with extra steps.
5. Failure buffer
A percentage of the subtotal that covers the jobs that fail. 3–5% for tuned PLA; 10–15% for ABS, tall parts, or anything you have not printed before. One failed eight-hour print wipes out the profit on several successful ones, and the buffer is what absorbs that.
Why filament-only pricing loses money
Take a realistic small job — 50 g of PLA, four hours, on a $699 printer:
| Line | Cost | Share |
|---|---|---|
| Filament | $1.00 | 23% |
| Electricity | $0.08 | 2% |
| Machine wear | $0.47 | 11% |
| Labour (10 min @ $15/hr) | $2.50 | 58% |
| Failure buffer (5%) | $0.20 | 5% |
| True cost | $4.25 | 100% |
Filament is 23% of the cost. Price this print at "$1 of plastic plus a bit" and every sale loses money. Price it off the $4.25 and a 50% margin puts it at about $6.40 — before platform fees take their cut.
Platform fees are not a rounding error
Selling through a marketplace changes the maths. As of 2026, Etsy stacks a $0.20 listing fee, 6.5% transaction fee, and 3% + $0.25 payment processing — roughly 10–11% all-in, and over 20% once off-site ads are triggered. eBay runs about 13.6% + $0.40. Amazon Handmade takes 15%. Pick your channel in the calculator and it shows what actually lands in your pocket.
Reading the result
- True cost — your floor. Never sell below it, and never quote from filament weight alone.
- Sell price — true cost plus your margin.
- What you keep — after the platform's cut. This is the only number that pays you.
- Per printer-hour — the sanity check. If a job nets $2/hour of machine time, the machine is better used on something else.
How accurate is it?
Volume is exact — it comes from summing signed tetrahedra over every triangle in your mesh, which is the same technique slicers use. Weight follows directly from volume and density, so it is accurate as long as your model is watertight (the tool warns you if it looks like it is not).
Time is the modelled part, good to roughly ±30%. It uses effective volumetric flow per printer class, calibrated against measured Benchy times, adjusted for layer height, material and supports. For quoting a customer that is comfortably good enough; for a 500-unit production run, slice it and use the real number. The Print Time Estimator uses the identical engine, so the two tools will always agree on the same file.
Frequently asked questions
How do I calculate the cost of a 3D print?
Add up five things: filament (weight × price per kg), electricity (watts × hours × your kWh rate), machine wear (printer price ÷ realistic lifetime hours × print hours), your labour (hands-on minutes × your hourly rate), and a failure buffer (3–15% of the subtotal). That total is your true cost. Most calculators only show the first one, which is typically under a quarter of what the print actually costs you.
Do I need to slice the file first?
No. Drop the STL in and the calculator reads the mesh directly — it computes exact solid volume from the triangles, then models the shell, infill and supports to get filament weight and print time. That is the whole point: you get a cost before you open a slicer.
Is my STL uploaded anywhere?
No. The file is parsed entirely in your browser using the File API — it never leaves your device and there is no server to send it to. You can check the Network tab in your browser devtools and watch nothing happen.
Why is the cost higher than just filament × price?
Because filament is usually the smallest line. On a typical 4-hour, 50 g print, filament might be $1.00 while your labour is $2.50, machine wear $0.47, failure buffer $0.30 and electricity $0.08. Pricing on filament alone is the single most common reason 3D printing side businesses quietly lose money.
How accurate is the print time?
Within roughly ±30% for typical parts. Time is modelled from effective volumetric flow rates per printer class, calibrated against measured Benchy times, then adjusted for layer height, material and supports. It is intentionally honest about being an estimate — for a production run of hundreds, slice it properly and use that number.
What failure rate should I use?
For a tuned printer running PLA, 3–5% is realistic. For ABS or ASA, tall or thin parts, or a model you have never printed before, budget 10–15%. The buffer is not pessimism — it is the pool that pays for the reprint when one job in twenty fails.
Does it account for Etsy and eBay fees?
Yes. Pick your sales channel and the calculator stacks the real 2026 fee structure — listing fee, transaction percentage, payment processing percentage and flat fee — then shows what actually lands in your pocket after the platform takes its cut.
What margin should I charge?
For hobby sellers, 50–100% over true cost is the normal range. Custom or one-off work supports 150–300% because it carries more uncertainty and more communication overhead. Set margin against cost, not against sale price — those are different numbers and confusing them is how thin margins happen.