Independent tools, transparent math.

SellerMath is a small, independently built project with one goal: help marketplace sellers understand what platforms actually charge, in plain numbers. We are not affiliated with Etsy, Shopify, eBay or any other marketplace, and we do not sell seller data, courses or "growth hacks".

How the tools are built

Every calculator is a static page that runs entirely in your browser. There is no backend processing of your inputs, no accounts, and no paywalls. The formulas on each page are written out in full so you can verify the arithmetic yourself — we would rather show the math than ask you to trust a black box.

How fee data is maintained

Fee rates are taken from official platform documentation (seller handbooks, pricing pages and fee schedules) and reviewed periodically. Each page shows the date its rates were last verified. Platforms change their fees from time to time, and individual accounts can have different terms, so our figures should be treated as planning estimates. If you spot a rate that has changed, we genuinely want to hear about it — see the contact page.

How the site is funded

The tools are free. The site is intended to be supported by unobtrusive advertising once it qualifies for an ad network. We do not accept payment to feature, rank or recommend any seller service.