Wire Resistance Calculator
Calculate Wire Resistance
Calculate wire resistance and voltage drop for electrical circuits. This calculator helps determine if your wire gauge is adequate for the circuit length and current load, ensuring safe and efficient electrical installations.
How Wire Resistance Calculator Works
Wire resistance increases with length and decreases with larger wire gauge. Understanding resistance is crucial for calculating voltage drop and ensuring circuits operate efficiently.
Key Factors Affecting Wire Resistance
- Wire Material: Copper has lower resistance than aluminum
- Wire Gauge (AWG): Larger numbers = smaller wire = higher resistance
- Length: Resistance increases proportionally with length
- Temperature: Resistance increases with temperature
- Conductor Cross-Section: Larger area = lower resistance
Voltage Drop Guidelines
NEC Recommendations:
- Maximum 3% voltage drop for branch circuits
- Maximum 5% voltage drop for branch circuits + feeders combined
- Voltage drops over 5% can cause equipment malfunction
- Higher voltage drops reduce efficiency and motor performance
Wire Material Comparison
| Property | Copper | Aluminum |
|---|---|---|
| Conductivity | Better | Lower |
| Weight | Heavier | Lighter |
| Cost | Higher | Lower |
| Corrosion Resistance | Better | Requires special care |
Temperature Effects
- Copper: Resistance increases 0.393% per °C above 20°C
- Aluminum: Resistance increases 0.403% per °C above 20°C
- Higher ambient temperatures require derating of current-carrying capacity
- Overloaded circuits generate heat, further increasing resistance
Practical Applications
- Circuit Design: Ensure adequate wire size for load and distance
- Motor Circuits: Minimize voltage drop to prevent motor damage
- Lighting Circuits: Prevent dimming due to voltage drop
- Panel Design: Calculate feeder sizes for electrical panels
- Code Compliance: Meet NEC voltage drop requirements
Safety Considerations
- Undersized wires can overheat and cause fires
- Excessive voltage drop can damage sensitive equipment
- Always consult local electrical codes
- Consider future load growth when sizing conductors
- Use proper termination methods for aluminum conductors
Cite this page as:
Daniel, P. Wire Resistance Calculator. Available at: https://constructioncalculators.com/wire-resistance-calculator/. Accessed: October 25, 2026.