How we build, review and correct our pages

Each calculator is a small, pure TypeScript function: the same inputs always give the same result, and nothing you type leaves your browser. Every function is covered by automated unit tests that check its output against reference values.

Rates, brackets and tables live in separate data files, each recording where the figures came from and the date they were retrieved or the date they apply from. Every calculator page explains how the result is calculated and shows a worked example produced by the same code that produces your result. The full list of formulas, data tables and assumptions is on the methodology page.

We prefer official and primary sources: the agency that sets a rule or publishes a statistic, or the standard that defines a unit. Where no official figure exists, we use a widely cited published reference and name it. The publishers cited across our calculators today are:

• Internal Revenue Service (IRS)
• U.S. Bureau of Labor Statistics (BLS)
• Consumer Financial Protection Bureau (CFPB)
• Federal Reserve
• Freddie Mac
• Federal Trade Commission (FTC)
• Centers for Disease Control and Prevention (CDC)
• National Institute of Standards and Technology (NIST)
• International Bureau of Weights and Measures (BIPM)
• U.S. Naval Observatory
• U.S. Department of Energy, Environmental Protection Agency and Energy Information Administration
• U.S. Securities and Exchange Commission (Investor.gov)
• National Association of Insurance Commissioners (NAIC)
• State departments of revenue and state legislatures
• Tax Foundation
• College Board
• NerdWallet (the needs-based method used in the life insurance calculator)
• Peer-reviewed research (for example, the Mifflin–St Jeor equation and the Trinity study)

Each page lists its own sources under “Sources” at the bottom, with links to the original documents.

Calculators are product pages, not individually “reviewed” articles. Each one uses sourced methods, automated unit tests, and data files that are updated when tax rules or other figures change. Jairo Tunisse maintains the code, the sources and those updates.

Guides and other editorial posts under /guides go through human review by Jairo Tunisse before they are marked published. Published guides show who wrote them and when they were reviewed.

Every calculator and guide page shows when its content or data was last updated (“Last updated”).

Tax tables are updated for each new tax year when the IRS publishes its inflation adjustments and when state figures change. Inflation data is updated when the Bureau of Labor Statistics publishes a new annual average, and any figure that is still an estimate is labeled as one. Other pages are updated when a source changes or an error is found. Every update changes the page’s “Last updated” date.

If you think a result or a figure is wrong, tell us through the contact form or by email at [email protected]. Please include:

• the page address (URL) of the calculator or guide;
• the inputs you entered;
• the result you expected, and why — ideally with a link to the source you are comparing against.

We check every report. When an error is confirmed, we fix the page and update its “Last updated” date.

4calcs may show ads. Ads never change a result: every calculation runs in your browser in code that has no connection to advertising, and advertisers have no say in what we publish. Any partner link will be clearly labeled. See our privacy policy for how ads and cookies work.

[conteúdo do Jairo]

Questions about this policy? Contact us. You can read more about who runs the site on the about page.