Electrical

Electrical Wire Sizing Calculator

Calculate ampacity and voltage drop for industrial wiring applications.

Input Parameters

Units:

Load Current

System Voltage

One-Way Distance

Circuit Type

Maximum Voltage Drop

Results

Enter circuit parameters and click Calculate

What is Electrical Wire Sizing?

Wire sizing determines the correct conductor size to safely carry the required current while keeping voltage drop within acceptable limits over the circuit length.

Undersized wire causes excessive voltage drop, wasted energy, and fire hazards. Proper sizing ensures efficient, safe, and code-compliant installations.

How to Use

Enter the load current in amperes
Select the system voltage
Enter the one-way distance to the load
Select single-phase or three-phase
Set maximum allowable voltage drop percentage
Click Calculate for recommended wire size

FAQs

Excessive voltage drop causes motors to run hot and inefficiently, lights to dim, and sensitive equipment to malfunction. NEC recommends 3% max for branch circuits and 5% total from service entrance. Some applications require even tighter limits.

AWG (American Wire Gauge) uses numbers where smaller = larger wire. mm² is the actual cross-sectional area. AWG 12 ≈ 3.31 mm², AWG 10 ≈ 5.26 mm². Europe and most of the world use mm² sizing.

Aluminum is cheaper and lighter but requires 2 sizes larger than copper for the same ampacity (e.g., aluminum #4 ≈ copper #6). It needs special terminations to prevent oxidation and loosening. Common for service entrances and feeders, less so for branch circuits.

Ampacity must be reduced (derated) for: more than 3 current-carrying conductors in a conduit, ambient temperatures above 86°F (30°C), and continuous loads (running 3+ hours). NEC provides specific derating factors.

Wire insulation ratings (60°C, 75°C, 90°C) determine ampacity. Higher temp ratings allow more current. However, you must use the lower rating of the wire OR the termination (usually 75°C for most equipment).

Limitations

• Based on copper wire at 75°C - adjust for aluminum or other temps
• Does not include derating for bundled conductors or high ambient
• Continuous loads may require additional 25% capacity
• Always verify with NEC tables and local code requirements
• Motor circuits have additional requirements (NEC Article 430)