About Calcamaze

Calcamaze is a growing library of free calculators for everyday questions — from loan payments and compound interest to BMI, concrete and unit conversions. Every calculator shows the formula it uses and a worked example, so you can check the answer yourself.

Editorial policy

Each calculator is built from established, published formulas. Its maths is covered by automated tests, including a test that the worked example in its article gives exactly the result shown.

Calculators marked “✓ Human verified” have also been checked by a named reviewer, who tried the calculator, checked its formula against an independent source and read the article for accuracy. The badge shows who reviewed it and when. If a calculator is changed after its review, the badge is removed until it has been reviewed again. Human review of the calculators is under way.

Results are estimates for general information. They are not financial, medical, legal or engineering advice — for decisions that matter, talk to a qualified professional.

Found a mistake?

We fix errors quickly. Contact us with the calculator, the inputs you used and the result you expected.

Accessibility

We aim to meet WCAG 2.2 level AA: every field has a label, results are announced to screen readers as they change, the site works with a keyboard, supports light and dark mode, and adapts to phone screens. If something is hard to use, please tell us.