Using undersized wire is a serious fire and safety hazard. Using oversized wire wastes money. Selecting the correct wire gauge for every electrical circuit is one of the most important decisions in any electrical project.
Understanding Wire Gauge (AWG)
In the US, wire size is measured in AWG (American Wire Gauge). Counterintuitively, a smaller AWG number means a thicker wire with higher capacity. 10 AWG is thicker and carries more current than 14 AWG.
Common Wire Sizes and Their Uses
| Wire Gauge | Ampacity | Common Use |
|---|---|---|
| 14 AWG | 15 amps | Lighting circuits, general outlets |
| 12 AWG | 20 amps | Kitchen outlets, bathrooms, general purpose |
| 10 AWG | 30 amps | Dryers, air conditioners, water heaters |
| 8 AWG | 40 amps | Ranges, EV chargers, large AC units |
| 6 AWG | 55 amps | Sub-panels, large appliances |
| 4 AWG | 70 amps | Service entrance, large sub-panels |
| 2 AWG | 95 amps | Main service entrance |
Voltage Drop: Why Wire Length Matters
Over long distances, thin wire causes voltage drop — the voltage at the end of the circuit is less than at the source. This causes dim lights, slow motors, and overheating. As a rule of thumb, increase wire size by one gauge for every 50 feet of circuit length beyond 100 feet.
Calculate the Right Wire Size
Enter your circuit amperage and length to get the correct wire gauge recommendation.
Use Wire Size Calculator →Wire Color Code (US Standard)
| Color | Purpose |
|---|---|
| Black | Hot wire (120V circuits) |
| Red | Hot wire (240V circuits, second hot) |
| White | Neutral wire |
| Green or bare copper | Ground wire |
| Gray | Neutral (sometimes used in conduit) |
Always follow local electrical codes and consider hiring a licensed electrician for any work involving the main panel or new circuits.