Electrical Calculators.
Wire, breakers, conduit and load — 7 tools, all free.
Conductor sizing against the NEC ampacity tables, voltage drop over a long run, conduit fill, a dwelling service load, generator sizing and a recessed-lighting layout. Each one prints the table and the article it read from, because an inspector will ask. These size and sanity-check a plan; they do not replace a licensed electrician or a permit.
Wire Size
AWG for the load and the run
Answer in AWGVoltage Drop
What a long run costs you
Answer in % dropConduit Fill
Trade size for the wires you pull
Answer in trade sizeService Load
100, 150 or 200 amp service
Answer in ampsGenerator
Running watts plus the surge
Answer in wattsRecessed Lighting
How many cans, and how far apart
Answer in fixturesWatts & Amps
The power triangle, solved
Answer in wattsThe reasoning behind them
Guides that cover the judgement calls these tools can't make for you — what to measure, which assumption to change, and where the money goes when an estimate is wrong.
The rest of the wall
Interior Calculators, Outdoor & Yard Calculators, Heating & Cooling Calculators — or all 18 in one list.