How we verify fee rates
A fee calculator is only useful if its numbers are the platform’s numbers today. Most calculators online were correct on the day they were published and never touched again. This page describes what Feenomics does differently, so you can decide how much to trust it.
1. Official sources only
Every rate comes from the platform’s or carrier’s own fee page, help article, seller policy or published price list. Third-party articles, forum posts and other calculators are never a source. Each calculator links the exact pages it was built from.
2. Every value is dated
Each rule in our database stores the official URL, the effective date the platform states (when it states one) and the date we last read the page. The “Rates verified” badge on a calculator shows the most recent check across the rules it uses. If a rule is awaiting re-verification, the badge says so instead.
3. Platform examples are replayed as tests
Where a platform publishes worked examples of its fees, those examples are encoded as automated tests. A change to any calculator cannot ship unless it reproduces every published example to the cent. Where a platform publishes no examples, we write our own from the rules and show one on the page so you can check the arithmetic yourself.
4. A scheduled re-check, not a hope
Each platform page is re-read on a schedule tied to when that platform tends to change fees: eBay around January to March and July, Etsy in spring, Amazon FBA in January, USPS in January and July, UPS and FedEx at their January general rate increases, and the resale apps whenever they announce changes. Between checks, reader reports are verified within days.
5. Changes are logged publicly
When a value changes, the change log records the platform, the old and new values, the effective date and the source. You can see what the calculator was using on any date.
What the calculators do not do
- They do not give tax, legal or accounting advice. Thresholds such as 1099-K reporting are described, never interpreted for your situation.
- They do not model every edge case: refunds, chargebacks, promotional credits, currency conversion on payouts and seller-specific negotiated rates are outside the standard schedules.
- They do not collect your sales data. Inputs stay in your browser and in the page URL if you choose to bookmark or share it.
Who maintains this
The Feenomics team builds and maintains the calculators and the rule database. Corrections are welcome through the contact page; a link to the official page showing the change is all that is needed.