About Voltacalc
Voltacalc is an independent publisher of electrical calculators. This edition is written for the United States: 120/240 V, AWG conductors, and the NEC as your authority having jurisdiction adopts it.
One engine, tool and text together
Every figure on this site comes out of the same TypeScript engine. The interactive tool calls it in your browser; the worked example under it is computed at build time by the same functions, from that edition’s own scenario. Prose and tool therefore cannot disagree - a stale hand-typed number has nowhere to hide.
The engine carries 261 unit tests and a second, independent battery of 411 checks written against golden values, dimensional analysis and rounding direction. Before each release a fault is injected on purpose to prove the battery still bites.
What this site will not do
It will not reproduce a standards table. The ampacity tables in NFPA 70 are a copyrighted work that NFPA sells; an ad-supported page that copies the series wholesale is not a citation, it is a substitute. You get the value your own inputs produced and the article it came from, never the table.
It will not invent a number to look complete. Where the current-carrying capacity for an installation method has not been verified from a source with a date, the calculator says the check was not made rather than quietly making one. Sizing here is voltage drop and standard ratings; ampacity, derating and the terminal temperature rating stay with the person who signs the job.
Not a substitute for an electrician
The calculators are a planning aid for people who already know what they are looking at: electricians, solar and EV installers, maintenance techs, and homeowners pricing a job before they call one. They do not carry your inspection, your load calculation or your permit. Work that touches a panel belongs to a licensed electrician, and the AHJ has the last word.
Corrections
If a result looks wrong, tell us with the inputs you used and we will check the engine against it in public. Corrections to a cited figure need a source and a date; that is the same bar the site sets for itself.
These calculators follow the NEC as it is published nationally. Local amendments are common and the authority having jurisdiction has the final say on your installation; permitted work must be inspected. Nothing here replaces a licensed electrician.