A fee calculator is only as good as its numbers. If the rate is a point out of date, every payout it shows is wrong, and you price your items wrong. So this is how the numbers here are kept honest.
Official pages only
Every rate comes from the platform's own fee page or help centre: eBay's selling fees pages, Etsy's fees and payments policy, Poshmark's fee policy, Mercari's help articles, and so on. Each calculator lists the exact pages it uses under Sources, with the date they were last checked. Other calculator sites and blog posts are useful for spotting that something has changed, but they never decide a number on their own. When we compared other fee calculators while building this site, several of them disagreed with each other and with the platforms, which is exactly why we don't copy from them.
A daily check of every source
Every morning an automated job opens every official fee page we rely on, pulls out the lines that mention fees, percentages or amounts, and compares them with the day before. If anything on those lines changes, it flags the page for review. A person then reads the change and updates the fee data. The calculators, fee tables, worked examples and comparison all read from that one data file, so an update reaches every page at once.
The job deliberately doesn't rewrite numbers by itself. Fee pages are full of examples, promotions and exceptions, and a script that guessed wrong would quietly publish bad numbers. A short delay is better than a wrong payout.
What the "last checked" date means
It's the date the calculator's rates were last confirmed against the platform's own pages, not the date the page was last edited. When the daily job reads every official page for a platform live and finds nothing changed, that confirms the rates and the date moves to that day. Pages that block automated reading, like some of eBay UK's help pages, are checked by hand instead, so their date moves when a person has read them. If fee data goes more than 45 days without a fresh check, it gets flagged for review.
What the calculators leave out
- Income tax. Profit here is before any income tax you owe on your sales.
- Account-specific discounts and penalties. Some platforms change your rate based on seller level, performance or promotions. Where it's a simple option (like eBay's Promoted Listings rate or StockX seller level) the calculator lets you set it. Where it depends on your account history, we explain it on the page instead.
- Currency conversion. If you sell in a different currency from your bank account, platforms usually charge a conversion fee on top.
Spotted a wrong number?
Platforms sometimes change fees with little notice, and some changes reach different sellers at different times. If your statement doesn't match a calculator here, tell us which platform and what you were charged. Every report gets checked against the official page, and the fee change log records what changed and when.