Free Wire Gauge Calculator (AWG & mm²)

Sizing electrical wire correctly is the most critical step in ensuring equipment runs safely and efficiently. If a wire is too small, it can overheat and cause a fire, or create excessive voltage drop that damages your devices. Our professional Wire Gauge Calculator instantly finds the perfect AWG and mm² wire size based on your specific load, distance, and National Electrical Code (NEC) derating requirements.

How to Use the Calculator

1. Enter Core Electrical Data: Input your load current (in Amps) and the source voltage at the breaker panel.
2. Input the Distance: Enter the one-way distance from the power source to the load. You can easily toggle between Feet and Meters.
3. Set Voltage Drop Limit: The default and highly recommended standard for branch circuits is 3%. You can adjust this up to 15% for specific applications (like starting motors).
4. Select Material and Phase: Choose between Copper or Aluminum conductors, and select whether your system is DC, Single-Phase AC, or 3-Phase AC.
5. Apply Advanced Settings (Optional): Click "Show Advanced NEC Settings" to apply environmental derating factors. You can adjust for high ambient temperatures, running multiple wires in the same conduit, or applying a 125% safety factor for continuous loads (loads running for more than 3 hours).
6. Instant Results: Because this calculator processes in real-time, your recommended AWG wire size, mm² equivalent, and exact power loss will appear instantly as you type! Use the Copy Results button to save the specs for your project.

The Engineering Formulas

This tool determines the optimal wire size by running a loop that checks both Ampacity Limits (using NEC 310.16) and Voltage Drop Limits. The formulas used to find the voltage drop are:

• Single Phase & DC: V_drop = (2 × L × I × R) / 1000
• Three Phase: V_drop = (√3 × L × I × R) / 1000
• Where L = length in meters, I = current in Amps, and R = resistance per km.