Disclaimer

MicroCoulomb is an educational and reference site, and its calculators give theoretical results. They do not replace the National Electrical Code, the manufacturer instructions for a device, or the judgment of a licensed electrician, and nobody should size wiring or protective devices from these results alone.

Electrical work is dangerous

Mains voltage can cause serious injury or death. Work on installations must be done by a qualified, licensed person following the National Electrical Code and local rules. Always switch off and verify that a circuit is dead before touching it.

Results are theoretical

The formulas assume ideal conditions, such as balanced three-phase loads and the power factor you enter. Real devices differ. Use the rating on the device label for the actual current and power.

No professional advice

Nothing on the site is engineering, legal or safety advice. See also the terms of use and the about page.

External names

Standards, organizations and brand names mentioned belong to their owners. MicroCoulomb is independent and not affiliated with them.

Frequently asked questions

Can I use the calculators to size a breaker?

Use them for a first estimate only. Breaker and wire sizes follow the NEC and a licensed electrician.

Are the results exact?

They are exact for the formulas shown, but real devices differ from ideal conditions.

Is the site affiliated with any standards body?

No. It cites public standards such as the BIPM SI Brochure and NIST publications.