About

A small studio that makes pricing tools for people who sell 3D prints

Spool & Margin is a small, anonymous studio. We make one kind of thing: spreadsheets and calculators that tell you what a print really costs and what to charge for it.

What we make

• The online calculator on this site. Free, no sign-up, one product at a time.
• 3D Print Price Checker (Lite). A free spreadsheet for Excel and Google Sheets that checks up to ten products at once.
• 3D Print Business System ($14, one-time). A workbook for the whole operation: several printers, plate printing, two-color prints, orders, filament stock, failed prints, quotes and a dashboard with profit per printer hour.

The spreadsheets are sold and delivered through Gumroad, which handles the checkout. This site does not take payments.

Built with AI assistance

We say this plainly because you should know it. The spreadsheets, this website and the texts on it were built with the help of AI tools, under human direction. We do not publish reviews or testimonials we did not receive, and we do not quote statistics we cannot source. Where a guide uses example numbers, it says so.

How the formulas are tested

• Every formula in the spreadsheets is checked against an independent calculation model before a version is released.
• The calculator on this site uses the same formulas as the free spreadsheet. An automated test compares its results with the spreadsheet's sample products, to nine decimal places, and checks edge cases such as missing inputs and impossible settings.
• The guides use the same sample numbers, so every figure in them can be reproduced in the calculator.

Tested does not mean infallible. If you find a result that looks wrong, please tell us through our Gumroad page.

A calculation tool, not financial advice

The tools do arithmetic on the numbers you enter. The printer life, failure rate, labor rate and fee values are your assumptions, and the examples and defaults are placeholders, not recommendations. Nothing here is tax, legal, accounting or financial advice. Marketplace fees in the guides are summaries with a date; the marketplace's own pages are the authority. You are responsible for your prices.

Privacy

• Our pages set no cookies and load no analytics, advertising scripts, fonts or other files from outside the site. More on the privacy page.
• The calculator runs in your browser. The values you type are saved in your browser's local storage so they are there on your next visit. They are never sent to us or to anyone else. The "Reset" button deletes them.
• Links to Gumroad carry a short tag (utm_source=site) that tells us a visit came from this website. It contains nothing about you.
• The company that hosts this site may keep standard server logs, as every web host does.