⚡Electrical

Wire Size Calculator

Determine the correct wire gauge based on amperage, distance, voltage, and conductor material.

Calculate Wire Size

Load Amperage (A)

One-Way Distance (ft)

System Voltage (V)

Conductor Material

Phase

Max Voltage Drop (%)

How Wire Size Is Determined

The correct wire size depends on two factors: ampacity (the wire must safely carry the load current without overheating) and voltage drop (the wire must deliver adequate voltage to the load at the required distance).

NEC Guidelines

NEC 210.19(A)(1): Branch circuit conductors must have an ampacity not less than the maximum load.
NEC 215.2(A)(1): Feeder conductors shall have an ampacity not less than required to supply the load.
NEC 310.16: Ampacity tables for conductors rated 0–2000V.
Voltage Drop: NEC recommends no more than 3% for branch circuits and 5% total (feeder + branch).

Copper vs. Aluminum

Copper has about 61% of the resistance of aluminum for the same gauge, making it more efficient. However, aluminum is significantly cheaper and lighter, making it common for large feeders and service entrance cables. When using aluminum, you typically need to go up 1–2 wire sizes compared to copper.