About Seller Sum

Seller Sum is free fee and profit calculators for online sellers — eBay, Etsy, PayPal, Stripe, Square and more. It exists because the most-used fee calculators on the web run on stale numbers and hide who maintains them.

Who runs this

I'm Felix Oluwakeye. Owner of a cross-border print e-commerce business; Cloud FinOps specialist. I build these calculators because I use them. Fees are not an abstraction to me — they come off my own margins every week, in two countries.

How the numbers stay right

• One source of truth. Every rate lives in a single versioned data file with the official source URL and a verbatim quote from it. Calculators, fee tables and the changelog all render from that file — they cannot disagree.
• Tested against the marketplaces' own examples. Where a platform publishes worked examples (eBay does), our test suite reproduces them to the cent. Where they don't, tests assert the exact published rate text. A fee update that breaks a test doesn't ship.
• Dated, visibly. Every page shows when its numbers were last verified against the official source, and the changelog records what changed and when.

How this site makes money

Some pages recommend tools through affiliate links (always disclosed in-place). We may add unobtrusive ads later. Neither changes the numbers: rates come from the marketplaces' official pages, quoted and dated, whether or not there's a commission anywhere near them.

Found a discrepancy? The fee pages change quietly and we'd rather hear it twice than miss it once — check the changelog for the current verification dates.