| Gauge | Ampacity | Max breaker | Ω/1000ft | Diameter | Common use |
|---|---|---|---|---|---|
| 14 AWG | 15A | 15A | 3.140 | 0.064" | Lighting, outlets (15A circuits) |
| 12 AWG | 20A | 20A | 1.980 | 0.081" | Kitchen, bathroom (20A circuits) |
| 10 AWG | 30A | 30A | 1.240 | 0.102" | Dryers, A/C, water heaters |
| 8 AWG | 40A | 40A | 0.778 | 0.128" | Ranges, EV chargers, hot tubs |
| 6 AWG | 55A | 60A | 0.491 | 0.162" | Subpanels, large A/C |
| 4 AWG | 70A | 70A | 0.308 | 0.204" | Large subpanels, EV fast charge |
| 3 AWG | 85A | 90A | 0.245 | 0.229" | Feeders |
| 2 AWG | 95A | 100A | 0.194 | 0.258" | 100A service feeders |
| 1 AWG | 110A | 110A | 0.154 | 0.289" | Feeders, large subpanels |
| 1/0 AWG | 125A | 125A | 0.122 | 0.325" | 125A service, large feeders |
| 2/0 AWG | 145A | 150A | 0.097 | 0.365" | 150A service |
| 3/0 AWG | 165A | 175A | 0.077 | 0.41" | 175–200A service |
| 4/0 AWG | 195A | 200A | 0.061 | 0.46" | 200A main service |
| 250 kcmil | 215A | 225A | 0.051 | 0.52" | 225A service |
| 300 kcmil | 240A | 250A | 0.043 | 0.57" | Large commercial feeders |
| 350 kcmil | 260A | 300A | 0.037 | 0.616" | Large commercial feeders |
| 400 kcmil | 280A | 300A | 0.032 | 0.659" | Large commercial feeders |
| 500 kcmil | 320A | 400A | 0.026 | 0.736" | 400A+ service, large commercial |
Selecting the correct wire gauge is one of the most critical decisions in any electrical installation. Undersized wire creates resistance, generates heat, and can cause fires. Oversized wire wastes money. NEC ampacity tables provide the authoritative answer for every common installation scenario — this tool puts that data at your fingertips without hunting through the codebook.
Understanding AWG. AWG numbers run counterintuitively — the larger the number, the thinner the wire. 14 AWG is thinner than 12 AWG, which is thinner than 10 AWG. Common residential gauges are 14 AWG (15-amp circuits), 12 AWG (20-amp circuits), and 10 AWG (30-amp circuits). For large appliances like electric ranges and EV chargers, 6 AWG or heavier is typically required.
Copper vs. aluminum wiring. Copper has lower resistance and higher ampacity per gauge than aluminum. It is the standard for residential branch circuits. Aluminum is lighter and less expensive, widely used for large-feeder and service entrance conductors. Aluminum used in branch circuits requires special connectors rated for aluminum to prevent oxidation and fire hazards. For a given ampacity, aluminum must be upsized two gauges compared to copper.
Temperature ratings and derating. NEC ampacity tables show three temperature columns: 60°C, 75°C, and 90°C. Use the 75°C column for most applications — most breaker panels and devices are rated 60 or 75°C even if the wire insulation is rated 90°C. Bundling multiple conductors in conduit requires ampacity derating per NEC 310.15.
Conduit fill and installation method. Ampacity varies by installation method. Wire in conduit dissipates heat differently than wire run through open air or buried in insulation. NEC Table 310.16 covers conductors in conduit, cable, or directly buried. Wires routed through insulated walls or attics may require derating due to elevated ambient temperature.
When to consult a licensed electrician. This tool is a reference for understanding and planning. For any permitted electrical work, a licensed electrician should perform the installation and a licensed inspector verify it. Electrical code compliance is non-negotiable — improper wiring is a leading cause of residential fires. Use this tool to educate yourself and verify quotes, but do not use it as a substitute for licensed professional work.