Sources we use
We rely on primary sources: each platform's published fee schedule and help center for its fees; the card networks' own interchange publications and the Federal Reserve for card costs; the IRS, U.S. Census Bureau, Bureau of Labor Statistics and SBA for definitions and statistics; and university datasets and open textbooks for formulas and industry benchmarks. We do not use seller forums, marketing posts or other calculator sites as sources of fact.
How calculators are checked
Every calculator uses published, standard formulas. The code is covered by automated tests that check known answers (for example, an item that costs $60 and sells for $100 has a 40% margin and a 66.7% markup, and a business with $15,000 of fixed costs and a $20 contribution per unit breaks even at 750 units). We show the formula next to each tool so anyone can verify the result by hand.
What we will not publish
- Recommendations to sell on, or avoid, a particular platform, and rankings paid for by anyone.
- Affiliate links, referral codes, coupons or sponsored reviews.
- Claims we cannot support with a source.
Updates and corrections
Each page shows the date it was last updated. When a platform changes its fees or an official statistic is revised, we update the affected calculators and pages and add the change to that page's fee log. If you find an error, tell us through the contact page and we will review it and correct it.