Wire Size Calculator

Wire size is calculated based on the circuit's amperage, voltage, distance, and allowable voltage drop. The calculator determines the minimum AWG size that can safely carry the current while staying within voltage drop limits per NEC standards.

Aluminum wire has higher resistance than copper, so it requires a larger gauge (lower AWG number) to carry the same current safely. Aluminum is lighter and less expensive but requires special connections and installation practices.

The NEC recommends maximum 3% voltage drop for branch circuits and 5% for feeders. Lower voltage drops provide better performance but require larger, more expensive wire. Most residential circuits use 3% as the standard.

Longer wire runs have more resistance, causing greater voltage drop. As distance increases, you need larger wire (lower AWG number) to maintain acceptable voltage levels at the load. This is why long runs to outbuildings often require oversized wire.

Three-phase circuits are more efficient and have lower voltage drop for the same power transmission. The calculation formulas differ, with three-phase using √3 multiplier, resulting in smaller wire requirements for equivalent power delivery.

Yes, wire ampacity decreases at higher temperatures. The insulation temperature rating (60°C, 75°C, 90°C) affects the wire's current-carrying capacity. Higher temperature ratings allow smaller wire sizes for the same amperage.

Undersized wire can overheat, causing fire hazards, equipment damage, and code violations. It also causes excessive voltage drop, leading to poor equipment performance, motor damage, and increased energy costs.

Yes, using larger wire than calculated is always acceptable and often beneficial. Oversized wire reduces voltage drop, improves efficiency, runs cooler, and provides capacity for future load increases, though it costs more initially.