About CalcTools

Why this site exists

CalcTools is an independent project started in 2026 by Iliass A., a developer who got tired of calculator sites buried under pop-ups, sign-up walls and unexplained numbers. The goal is simple: a fast tool that gives the right answer, followed by a clear explanation of how that answer was reached and when it should not be trusted blindly.

How the calculators are built

Each calculator implements a published, standard formula — for example the WHO definition of BMI, the Mifflin-St Jeor equation for energy needs, the standard amortization formula for loans, or the exact definitions of imperial units from the 1959 international agreement.

Every formula is covered by an automated test suite that checks it against known reference values before each release. Unit conversion factors use exact legal definitions rather than rounded approximations.

How the content is written and reviewed

Explanations are written in English and French and reviewed by hand. Each page aims to answer the questions people actually have after getting a result: what the formula is, a worked example with real numbers, what the result means, and its limits. Pages show the date of their last review.

If you spot an error, an unclear explanation or a calculator you would like to see, please use the contact page — corrections are published quickly.

What CalcTools is not

Results are for information and education. Health calculators do not replace a medical consultation, and finance calculators do not replace personalized advice from a qualified professional or your lender's official offer.

Privacy and funding

Calculations run entirely in your browser; the values you type are never sent or stored. The site is free and is funded by optional Ko-fi donations and, where you consent, by advertising. See the privacy policy for details.