A manual, not a magic box
Online Calculators Free exists because most calculator sites hand you a number and hide the math. Here, every tool is a page in an open manual: the live result sits beside the substituted formula, a worked example, and an honest note about where the method breaks down.
How it's built
The whole site is static HTML. Every calculation runs in your browser — nothing you type is sent to a server, saved tools live in your device's local storage, and every visit loads fresh from the site.
Corrections
Formulas follow published standards (WHO, NIST, IRS instructions, textbook definitions) and each page names its method. If you find a number that disagrees with its stated formula, that's a bug and we fix it: see the repo link in the footer or the contact on the terms page.