It is not official NXP, IPC, or microcontroller documentation, and it does not certify a board. Formulas below are those published on the tool pages, checked against the usual textbook identities; a couple of worked examples on the site do not match those identities, and those examples are not repeated here.

Firmware and hardware people reach for browser calculators when a pull-up “usually works,” a debug UART is slightly corrupt, or a power trace looks narrow. Each problem has a published formula, assumptions, and things the formula cannot see: integer dividers, unmeasured bus capacitance, copper that is not exactly one ounce, and the far end of a serial link.

ResiCalc is an independent educational site of free, client-side electronics calculators. Its about page says results are for engineering guidance and should be verified against datasheets and standards for critical designs.…