Frank Numbers
Fed funds3.75%CPI3.5%30-yr fixed6.66%SS wage base$184,500401(k) limit$24,500

How we source these numbers

A calculator is only worth as much as the figures inside it. Here is exactly where ours come from, how they are checked, and what happens when we cannot confirm one.

The rule

Every figure carries its source

There are no bare numbers in this codebase. Every published figure is stored with the agency that issued it, the document it appears in, a link to that document, the date the rule took effect and the date we last checked it. That is why you see a line of small grey type under every rate on the site. It is not decoration, it is the figure’s provenance.

It also means a stale number is visible rather than invisible. If a rate has not been re-checked in months, the date says so.

Where they come from

United States sources

Whole set last reviewed August 1, 2026. The rates page lists all 9 figures individually.

State income tax is the one exception to reading every figure at its own primary source. Compiling fifty state revenue departments individually is not something we can keep current, so the state bracket tables come from the Tax Foundation’s annual compilation, which is cited on every paycheck result that uses it.

When we cannot confirm one

We say so, on the page

Sometimes a source is unreachable. When that happens the figure is marked unverified in the data itself, and every place it appears renders a visible warning instead of quietly presenting it as checked. A calculator that hides its uncertainty is worse than one that admits it.

How the maths works

Shown, not asserted

Every calculator has a “Show the math” panel with the formula, the bracket tables and the exact slice of your income that landed in each bracket. If you disagree with the answer, you can find the step you disagree with rather than arguing with a black box.

The calculation engines are pure functions with their own test suite. The federal bracket walks are checked against the cumulative “$X plus Y% of the excess” figures that the IRS publishes. Two independent routes to the same number, which is the point.

What we do not do

Your numbers stay on your device

Every calculation runs in your browser. Your salary, your balances and your contributions are never sent anywhere. There is no form submission to intercept and no server-side copy to leak. The privacy page sets out exactly what we do and do not collect.

Frank Numbers is an information tool. It is not tax, legal or financial advice, and it does not know about your specific circumstances. The caveats at the bottom of each calculator list what each one leaves out.