About this site
This site has free calculators for home electrical and power jobs: voltage drop, wire size, conduit fill, box fill, and watts to amps. They use US units and are written for US homes and shops.
Who builds it
I’m Ali. I build the calculators and write the pages myself. I’m not a licensed electrician, and no electrician has reviewed this site. I say that up front so you know what kind of help this is: careful math with its sources shown, not a professional’s sign-off on your job.
Where the numbers come from
The calculators work from physics and published data, not from rules of thumb:
- Physics. Ohm’s law, power from volts and amps, the resistance of copper and aluminum and how it changes with temperature, and the geometry of round wires inside round conduit.
- Maker data. Wire diameters, conduit inside sizes and box volumes come from manufacturers’ spec sheets and the published standards those makers build to.
- Two sources for every number. Before a figure goes live it has to match at least two published sources. Each calculator lists its sources at the bottom of the page.
The site doesn’t copy tables from the electrical code. When a result depends on a code rule, the page says so and tells you to check your code edition and your local inspector, the authority having jurisdiction (AHJ).
What it can’t do
A calculator can’t see your panel, your building or your town’s rules. The results are typical figures for planning and buying. They aren’t engineering or code advice, and they don’t replace a permit or an inspection. For the work itself, hire a licensed electrician.
Mistakes
If a number looks wrong, please tell me through the Contact page. I check the report against the sources, fix the page if it’s wrong, and update the date at the top.