1. What is a Wire Sizing Calculator by Southwire?

Definition: This calculator determines the minimum wire cross-sectional area needed based on electrical current, length, material resistivity, and allowable voltage drop.

Purpose: It helps electricians and engineers select properly sized wires to ensure safe and efficient electrical installations.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( A \) — Cross-sectional area of wire (m²)
• \( \rho \) — Resistivity of wire material (ohm-m)
• \( L \) — Length of wire (meters)
• \( I \) — Current flowing through wire (amps)
• \( VD \) — Maximum allowable voltage drop (volts)

Explanation: The formula calculates the minimum wire size needed to keep voltage drop within acceptable limits for a given current over a specified distance.

3. Importance of Proper Wire Sizing

Details: Correct wire sizing prevents excessive voltage drop, overheating, energy loss, and potential fire hazards while ensuring optimal system performance.

4. Using the Calculator

Tips: Enter the material resistivity (default 1.68×10⁻⁸ ohm-m for copper), wire length in meters, current in amps, and maximum allowable voltage drop in volts. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's the default resistivity value for?
A: The default 1.68×10⁻⁸ ohm-m is for copper wire at 20°C. Use 2.82×10⁻⁸ for aluminum.

Q2: Why is the length multiplied by 2?
A: The factor of 2 accounts for the round-trip length (both hot and neutral wires) in single-phase systems.

Q3: What's a typical allowable voltage drop?
A: For branch circuits, 3% is common (3.6V for 120V systems). For feeders, 2% is often used.

Q4: How do I convert m² to AWG?
A: Use our AWG Conversion Tool or refer to standard wire gauge tables that include cross-sectional areas.

Q5: Does this account for temperature effects?
A: No, for high-temperature environments, use adjusted resistivity values or consult NEC guidelines.