Free calculators for everyday money, work and dates

Twelve straightforward calculators. Each one shows the formula it uses, a worked example you can check by hand, and links to official sources. No sign-up, and your numbers never leave your browser.

How these calculators are built

Every calculator is plain HTML and JavaScript that runs on your device. We write out the formula on each page, test the code against hand-worked and published examples before each release, and link to the government or standards body pages the method comes from. If a result looks wrong to you, please let us know.

Money calculators give estimates for planning. For a decision that matters, confirm the numbers with your lender, employer, school or a qualified professional.