100 Amp Wire Size Calculator
Calculate proper wire size for 100 amp electrical systems with voltage drop analysis
Calculate Wire Size
Electrical current in amperes (typically 100A for this calculator)
Common voltages: 120V, 240V, 480V
Distance from power source to load (one-way)
Recommended: 3% for branch circuits, 5% maximum total
Copper has better conductivity but costs more
Three-phase systems are more efficient for high power
Typical: 30°C (ambient), 75°C (rated), 90°C (high temp)
Wire Size Results
Actual Voltage Drop: 0.00%
System Power: 19.2 kW
Material: Copper
System: Single-Phase
Category: No data - Enter values to calculate
⚠️ Safety Warnings
Example: 100A Service Panel
Given Parameters
Current: 100 A
Voltage: 240 V (single-phase)
Distance: 30 meters (98 feet)
Voltage Drop: 3% maximum
Material: Copper wire
Calculation
A = (2 × I × ρ × L × φ) / (V × %drop)
A = (2 × 100 × 1.68×10⁻⁸ × 30 × 1) / (240 × 0.03)
A = 1.008×10⁻⁴ / 7.2 = 1.4×10⁻⁵ m²
A = 14 mm² (recommended: 2 AWG)
Standard AWG Sizes
Material Properties
🔶 Copper
Resistivity: 1.68×10⁻⁸ Ω⋅m
Excellent conductivity, higher cost
⚪ Aluminum
Resistivity: 2.65×10⁻⁸ Ω⋅m
Good conductivity, lower cost, larger size needed
Voltage Drop Guidelines
3% max for branch circuits
5% max total (feeder + branch)
Lower is better for efficiency
Consider motor starting currents
Understanding Wire Size Calculations
Wire Size Formula
The wire cross-sectional area is calculated using Ohm's law and the voltage drop formula. The key equation considers current, distance, material resistivity, and acceptable voltage drop.
Key Variables
- •A: Wire cross-sectional area (mm²)
- •I: Current in amperes (A)
- •ρ: Material resistivity (Ω⋅m)
- •L: One-way wire length (m)
- •V: System voltage (V)
- •φ: Phase factor (1 or 1.5)
Calculation Formula
Wire Area: A = (2 × I × ρ × L × φ) / (V × %drop)
Voltage Drop: VD = (2 × I × ρ × L × φ) / A
Power: P = V × I × PF (single-phase)
Power: P = √3 × V × I × PF (three-phase)
Safety Considerations
• Always follow local electrical codes (NEC, CEC, etc.)
• Consider ambient temperature and wire bundling
• Account for continuous vs. intermittent loads
• Verify breaker and panel compatibility
• Use appropriate wire insulation ratings
Practical Applications
🏠 Residential Service
100A services typically use 2 AWG copper or 1/0 AWG aluminum for main feeders up to 100 feet.
🏭 Industrial Applications
Heavy machinery and motor loads require careful consideration of starting currents and power factor.
⚡ Sub-Panel Feeds
Sub-panels fed from main panels need proper wire sizing based on distance and load calculations.