How is a circuit sized?
Work out current from load and voltage, choose a conductor that meets ampacity and voltage-drop limits, and protect it with a breaker no larger than the wire allows. The NEC sets conductor ampacities and branch-circuit rules.
The calculators in this section do each step separately or together (wire size, EV charger).
Why does voltage drop matter?
On long runs, voltage at the load falls: motors run hot and draw more current, LED drivers misbehave, lights flicker and energy is lost as heat in the wire. The NEC recommends 3% on branch circuits and 5% total from service to outlet.
The fix is usually a larger wire, a shorter route or splitting the load across circuits.
What electrical work can I do myself?
Rules vary by jurisdiction; many require a licensed electrician, permit and inspection for new circuits. These calculators help you understand, price and check — they don't replace code compliance.
Always de-energize and test before touching conductors.