Free financial calculators,
built for accuracy

Sources first. Rules and rates come from official sources where we can use them — IRS publications, SSA and CMS figures, federal statutes such as the Homeowners Protection Act, and state revenue departments — and in some cases, such as combined state and local sales-tax rates, from the Tax Foundation. When a rate, threshold or rule changes, the new figure is recorded with its source and the date it was retrieved, and our Data Sources page lists where figures come from.

Tested math. The engines behind the tax, paycheck, Social Security and mortgage calculators, among others, are covered by test cases whose expected results were computed by hand or independently; a change that alters one of those results fails the build.

Drafting and review. Pages are researched and drafted with the help of AI tools. Proposed changes to the site go through a separate automated review, and new figures are checked against their sources. Hen owns the site and sets its direction.

Corrections. If you find an error, report it through the contact page; confirmed errors are corrected.

Formula accuracy. Every calculation is implemented against standard financial mathematics formulas. For loan calculations we use the standard amortization formula. For retirement projections we compound growth month by month.

Conservative defaults. Where we must choose a default input value we choose conservatively — for example, we use 7% as a default long-term stock market return (below the historical S&P 500 average of ~10%) to avoid overly optimistic projections.

Transparent assumptions. Every calculator page includes a "Limitations" section that explicitly states what the calculator does not model — tax impacts, variable rates, inflation adjustments, and so on.

Regular updates. Tax brackets, contribution limits, and standard rates change annually. We review and update affected calculators after each IRS announcement. Calculators tagged with a government data family show, under their title, the month those figures were last verified.