Each calculator is built from the published rules it models, such as IRS tables, Social Security Administration formulas and OPM retirement rules, and its maths is covered by automated tests. Results are still estimates. They depend on your inputs, on assumed returns and inflation, and on simplifications that each calculator explains.
Where the numbers come from
Every calculator has a methodology page listing its sources and assumptions. Figures that change every year, such as tax brackets, contribution limits and RMD tables, are taken from the primary source rather than from other financial websites.
Known limits
Assumed investment returns are not forecasts. Change them and the answer changes.
Tax calculations simplify. Most model federal brackets and the standard deduction, and only some include state tax.
Rules change. Check the year a calculator's figures come from before relying on a result.
A calculator may not cover an unusual situation. Each calculator's methodology page lists its formulas, assumptions and sources.
When we get something wrong
Errors are fixed in the calculation and the page text together, and material corrections are noted on the affected page.
This page is for educational purposes only and does not constitute financial advice. It is general information, not a recommendation for your situation. Consult a licensed financial advisor, tax professional, or attorney before acting on it. Full disclaimer →