Wire Gauge Calculator
Determine the correct wire size (AWG) for electrical installations based on current and voltage drop.
This calculator includes a 25% safety factor for current, as recommended by NEC for continuous loads.
Understanding Wire Gauge Selection
Selecting the proper wire size (AWG - American Wire Gauge) is critical for the safety and efficiency of electrical installations. Two primary considerations determine wire gauge selection:
Current Capacity
Wires must be sized large enough to carry the expected current without overheating. Undersized wires can cause:
- Fire hazards due to overheating
- Insulation failure
- Premature circuit breaker tripping
Voltage Drop
For longer runs, voltage drop becomes important. Excessive voltage drop can cause:
- Poor equipment performance
- Motor overheating
- Lighting dimming
- Reduced efficiency
Wire Gauge Facts
- Wire gauge numbers work in reverse - the smaller the number, the larger the wire
- Each 3-gauge decrease approximately doubles the wire's cross-sectional area
- Copper has about 1.6× better conductivity than aluminum
- The NEC recommends limiting voltage drop to 3% for branch circuits
National Electrical Code (NEC) Guidelines
While this calculator provides recommendations, always consult the latest NEC code and local regulations for specific requirements. Some important NEC guidelines:
| Circuit Type | Minimum Wire Size |
|---|---|
| 15A Branch Circuit | 14 AWG Copper / 12 AWG Aluminum |
| 20A Branch Circuit | 12 AWG Copper / 10 AWG Aluminum |
| 30A Branch Circuit | 10 AWG Copper / 8 AWG Aluminum |
| 40A Branch Circuit | 8 AWG Copper / 6 AWG Aluminum |
| 50A Branch Circuit | 6 AWG Copper / 4 AWG Aluminum |
Special Considerations
- Temperature rating: Wire insulation type affects current capacity
- Installation method: Conduit vs. free air affects heat dissipation
- Wire bundles: Multiple wires in the same conduit require derating
- Ambient temperature: Hot environments reduce current capacity
- Future expansion: Consider upsizing for potential future needs
Professional Assistance
While this calculator provides a good starting point, complex installations should be reviewed by a professional electrician or engineer.
Always follow local electrical codes, which may have specific requirements beyond the general guidelines provided here.
Recommended Maximum Voltage Drop
- Branch circuits: 3%
- Feeder circuits: 2%
- Combined: 5%
Critical Applications
- Motors: 3% starting, 1% running
- Electronic equipment: 1.5-2%
- LED lighting: 2% maximum
Reducing Voltage Drop
- Increase wire size
- Reduce circuit length
- Use higher voltage systems
- Use copper instead of aluminum