About Engineering Bible

Engineering Bible is a free library of engineering calculators written by Christos Papandreou. Every page gives the number, shows the formula and its assumptions, and works an example you can check by hand.

How the numbers are checked

The site holds 115 calculators, backed by 944 recorded checks and 442 cited sources. Each check compares a result with a textbook, standard or hand calculation, and a new version is published only if every check passes. Each calculator page has a button that runs its checks in your own browser, so you can watch them pass.

Assumptions and limits are stated on each page. A simplified formula is labelled as one, and calculators that follow a standard name it.

Report an error

If a number looks wrong, write to contact@engineeringbible.com with the page and the inputs you used. Every calculator has a Report a problem link and a share link that records your inputs.