Ohmetry is a set of free electrical, solar and protection calculators. Each one shows its formula, names the standard it follows, and includes a worked example you can check by hand.
Who builds it
Ohmetry is built by Amin, an electrical protection engineer with medium- and high-voltage experience under IEC and Saudi practice. Day to day, the work is the kind these calculators cover: cable sizing, voltage drop, short-circuit levels, and relay settings and grading. I built Ohmetry because the quick checks I kept doing by hand or in scattered spreadsheets deserved one place where the formula, the assumptions and the standard clause are all visible.
Standards
The NEC-based calculators follow the current NEC edition (2023). The code tables behind them were entered from the 2020 edition and checked value by value against a licensed copy of the NEC 2020; where 2023 changed a table number or a rating, the page says so. Protection calculators use IEC 60255-151 for relay curves and IEC 60909 for short-circuit levels. The methodology page lists the formulas and conventions.
How results are checked
Every formula has automated test cases with hand-calculated expected values, and the tests run before each release. If you find a wrong value or formula, please tell me: corrections are published on the corrections log.
What Ohmetry is not
These are estimating and checking tools. They do not replace a design by a qualified engineer, and local codes and the authority having jurisdiction take precedence. See the disclaimer.
Questions or corrections: contact.