Electrical Calculators

Installation and power distribution: conductor sizing, voltage drop, conduit fill, motor loads and three-phase maths. 19 calculators. The bench-level component side lives under Electronics.

Anything you would actually wire needs to satisfy your local code, and these pages do not know which code that is. Use them to size a first guess and to check somebody else’s numbers.

Voltage drop is the calculation that decides most long runs, and the constraint is usually drop rather than ampacity. A conductor can be rated for the current and still be the wrong size, because a 3% drop on a branch circuit or 5% total is the practical target. On a 30 metre run at 20 amps that frequently pushes you a gauge or two above what the ampacity table alone would allow. Undersized runs to a shed or a garage are the classic version of this.

Conduit fill uses the published fill percentages, and the number surprises people: 40% for three or more conductors, not the intuitive 70 or 80. The limit is about heat dissipation and about being able to pull the cable without stripping insulation, not about whether the wires physically fit.

Three-phase pages ask whether the load is wye or delta rather than assuming, since the root-three factor lands in a different place for each.