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Complete American Wire Gauge (AWG) reference with diameter, ampacity, resistance, and weight specifications. Use this chart to select the correct wire size for your electrical projects based on NEC requirements.
This table covers wire gauges from 4/0 AWG (largest common residential/commercial) to 40 AWG (fine magnet wire). Data based on solid copper conductors at 20C (68F).
| AWG | Diameter (in) | Diameter (mm) | Circular Mils | Cu 60C (A) | Cu 75C (A) | Cu 90C (A) | Al 75C (A) | Ohms/1000ft | lbs/1000ft |
|---|
Ampacity values per NEC Table 310.16 for conductors in raceway or cable. Actual ampacity depends on installation conditions, ambient temperature, and conductor count.
| Circuit Type | Breaker Size | Copper Wire | Aluminum Wire | Common Uses |
|---|---|---|---|---|
| General Lighting | 15A | 14 AWG | 12 AWG | Lighting circuits, low-draw outlets |
| General Purpose | 20A | 12 AWG | 10 AWG | Kitchen, bath, garage outlets |
| Heavy Appliance | 30A | 10 AWG | 8 AWG | Dryer, small welder, water heater |
| Range/Large Equipment | 50A | 6 AWG | 4 AWG | Electric range, large welder |
| Subpanel Feeder | 60A | 6 AWG | 4 AWG | Workshop subpanel, detached garage |
| Subpanel Feeder | 100A | 3 AWG | 1 AWG | Large workshop, addition |
| Cord Length | Up to 7A | 7-10A | 10-12A | 12-15A |
|---|---|---|---|---|
| 25 ft | 18 AWG | 18 AWG | 16 AWG | 14 AWG |
| 50 ft | 18 AWG | 16 AWG | 14 AWG | 12 AWG |
| 100 ft | 16 AWG | 14 AWG | 12 AWG | 10 AWG |
| 150 ft | 14 AWG | 12 AWG | 10 AWG | 10 AWG |
Extension cord gauge should limit voltage drop to 5% or less for proper equipment operation.
| Speaker Impedance | Up to 25 ft | 25-50 ft | 50-100 ft | 100+ ft |
|---|---|---|---|---|
| 4 Ohm | 16 AWG | 14 AWG | 12 AWG | 10 AWG |
| 6 Ohm | 18 AWG | 16 AWG | 14 AWG | 12 AWG |
| 8 Ohm | 18 AWG | 16 AWG | 14 AWG | 12 AWG |
Speaker wire gauge affects power transfer. Keep total cable resistance under 5% of speaker impedance for best audio quality.
| Application | Current Draw | Short Run (<3ft) | Medium Run (3-7ft) | Long Run (7-15ft) |
|---|---|---|---|---|
| LED Lights | 1-5A | 18 AWG | 16 AWG | 14 AWG |
| Auxiliary Lights | 5-10A | 16 AWG | 14 AWG | 12 AWG |
| Horns/Relays | 10-15A | 14 AWG | 12 AWG | 10 AWG |
| Fuel Pump | 15-20A | 12 AWG | 10 AWG | 8 AWG |
| Electric Fan | 20-30A | 10 AWG | 8 AWG | 6 AWG |
| Winch | 100-400A | 2 AWG | 1/0 AWG | 2/0 AWG |
| Battery Cable | 200+A | 4 AWG | 2 AWG | 1/0 AWG |
Automotive applications use stranded wire for flexibility. Add fuse protection at the battery for all circuits.
Voltage drop becomes significant on longer wire runs. This table shows the maximum one-way distance in feet for various wire gauges to maintain voltage drop under 3% for 120V and 240V circuits.
| AWG | 120V Circuit (feet) | 240V Circuit (feet) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 10A | 15A | 20A | 30A | 50A | 10A | 15A | 20A | 30A | 50A | |
Distances shown are one-way (panel to load). For 5% voltage drop, multiply distances by 1.67. Values based on copper conductors at 75C.
Use our wire size calculator for precise recommendations based on your specific requirements including voltage, amperage, distance, and acceptable voltage drop.
Wire Size CalculatorFor a 20 amp circuit, you need a minimum of 12 AWG copper wire or 10 AWG aluminum wire per NEC requirements. For longer runs over 50 feet, consider upsizing to 10 AWG copper to minimize voltage drop. Always use wire rated for the installation environment (NM-B for dry locations, THWN for wet locations or conduit).
AWG (American Wire Gauge) is a standardized wire gauge system where smaller numbers indicate larger wire diameters. The scale is logarithmic - every decrease of 3 AWG doubles the cross-sectional area. Circular mils (CM) measure the cross-sectional area of wire - one circular mil equals the area of a circle with a diameter of one mil (0.001 inch). Larger AWG wires like 4/0 are often specified in MCM or kcmil (thousand circular mils) for easier reference. For example, 4/0 AWG equals approximately 212,000 circular mils or 212 kcmil.
Wire ampacity increases with higher temperature ratings because the insulation can safely withstand more heat from current flow. A 12 AWG copper wire rated at 60C (NM-B cable) can carry 20 amps, while the same wire rated at 75C (THWN) can carry 25 amps, and at 90C (THHN) can carry 30 amps. However, the circuit's ampacity is limited by the lowest-rated component in the circuit - typically the device terminals rated at 60C for 100A or less circuits, or 75C for larger circuits. This means even with 90C wire, you often cannot use its full ampacity rating.
Aluminum has about 61% of the conductivity of copper, so it requires a larger cross-sectional area to carry the same current safely. For example, where 6 AWG copper is rated for 55 amps at 60C, you would need 4 AWG aluminum for comparable ampacity at 40 amps (or 4 AWG copper-clad aluminum). Aluminum is often used for larger feeders and service entrance cables due to significant cost savings despite the larger size requirement. Aluminum requires special anti-oxidant compound and AL-rated connectors to prevent connection failures.