About NumberBench

NumberBench is a growing library of free, no-nonsense calculators for money, home projects, health, business, and manufacturing decisions. Each tool answers one question clearly, shows the formula behind the result, and works instantly on any device.

What we believe

A good calculator should be fast, transparent, and private. Every NumberBench tool runs entirely in your browser — your inputs are never sent to us or stored — and each one explains how it reached its answer with a plain-English formula, a worked example, and notes on common mistakes.

How we build and review

Our calculators use standard, documented formulas and sourced data, with the public source linked on each calculator so you can verify it yourself. State income-tax tools use the latest published brackets from the Tax Foundation; finance tools use standard time-value-of-money math; health tools use established equations. We review rate-sensitive data at least once a year. Read our full methodology and review process.

Who is accountable

Keith Gilligan is the founder and editor of NumberBench. He oversees calculator design, benchmark research, sourcing standards, the review process, and corrections. Selected flagship pages carry his named byline; pages credited to the NumberBench editorial team follow the same published methodology.

We name an outside professional only after that person has reviewed the specific tool. Higher-stakes clinical and toxicity tools without a named credentialed reviewer remain available for reference, but are not submitted for search indexing until that review is complete.

How NumberBench is funded

The tools are free. We keep them that way through advertising and the occasional affiliate recommendation for products we think are genuinely useful — see our privacy & affiliate disclosure. Ads and affiliate links never change a calculator’s math.

Suggest a calculator

Want a tool we don’t have yet, or spot a number that looks off? Tell us — requests and corrections shape what we build next.

Corrections policy

Email [email protected] with the page, the inputs you used, and what appears wrong. We check the formula and cited source, correct warranted errors, and update the page’s review date when the underlying content changes.