About

This site is a collection of free, focused calculators — each one built around a single question, like body mass index, a loan payment, or compound interest — with the formula and reasoning shown alongside the result.

Most calculator sites hand you a number and stop there. Every calculator here also explains the formula behind that number and how the inputs feed into it, so you can check the math yourself instead of taking the result on faith.

The site is written separately in English, Korean, Japanese, German, and Spanish. Each language version is authored and checked on its own rather than generated by running one language through a translator, so explanations read naturally rather than literally.

This is a small, independent, statically generated site with no backend server, no user accounts, and no database. Every calculation runs in your browser. See the Privacy Policy for details on what that means for your data.

This site is built and maintained by an individual, not a company.