About CalcWisp
CalcWisp is an independent project based in Belgium that builds free, fast, private online tools: 60 calculators, converters and generators for money, school, health, work and files. Every tool runs in your browser, needs no account and shows how the answer was calculated.
How we build and check every calculator
- Formulas from primary sources. Financial limits come from official publications (for example IRS notices for retirement-account limits), health formulas from the original peer-reviewed equations (Mifflin-St Jeor for BMR, the US Navy circumference method for body fat), and math from standard definitions.
- Unit-tested against reference values. The calculation behind each tool lives in its own module with automated tests that compare results to known answers (worked textbook examples, official tables, or an independent calculation). Every change to the site has to pass all tests before it goes live.
- The working is shown. Wherever it helps, a tool displays the formula and steps so you can check the result yourself instead of trusting a black box.
- Dated and maintained. Each tool and guide shows when it was last updated. Year-specific numbers (contribution limits, tax thresholds) are reviewed when new figures are published.
How we write guides
Our guides explain the math behind everyday numbers. Each one answers the question first, uses worked examples with real numbers, links to the sources it relies on, and points to the matching free tool so you can try it with your own figures. Guides are educational and are not personal financial, medical or legal advice.
Privacy
Calculators and file tools run entirely in your browser: what you type and the files you open are never uploaded. See the privacy policy for the few exceptions (such as the optional paid resume report).
How CalcWisp is funded
The tools are free. The site is supported by advertising, by optional paid extras (a detailed resume rewrite report and Excel planners), and in some places by affiliate links, which are always labelled. None of these change how a calculation works.
Found a mistake?
Accuracy matters more to us than anything else. If a result or a figure looks wrong, tell us via the contact email on our Chrome extension listing or the receipt of any purchase, and we will check it against the source and fix it.