Our Methodology
Calculators are only useful if you can trust the math behind them. Here is how we approach accuracy and transparency.
Formulas are shown, not hidden
Every calculator displays the formula behind its result, so you can see exactly how your numbers were used.
Assumptions are stated clearly
Where a calculation relies on an assumption — like how a fee is applied — that assumption is written next to the result, not buried in fine print.
Calculations are tested
The math behind each calculator is checked against worked examples before it is published.
External data is sourced and dated
Where a calculator eventually uses reference data such as marketplace fees, that data will link to its official source and show the date it was last checked — and you will always be able to edit it with your own numbers.
Calculators are reviewed when formulas change
Each calculator page shows the date it was last reviewed. If its formula changes, the page is checked again before the update goes live.
Calculators on this site provide estimates for general informational purposes only, based on the numbers you enter and the assumptions stated on each page. They are not professional financial, tax, legal, or accounting advice. This page will be expanded as more calculators are published.