14 AWG 12 AWG 10 AWG 8 AWG 6 AWG 4 AWG 3 AWG 2 AWG 1 AWG 1/0 AWG 2/0 AWG 3/0 AWG 4/0 AWG 250 kcmil 300 kcmil 350 kcmil 400 kcmil 500 kcmil 600 kcmil 700 kcmil 750 kcmil 800 kcmil 900 kcmil 1000 kcmil 1250 kcmil 1500 kcmil 1750 kcmil 2000 kcmil

Single-Phase Three-Phase

60°C 75°C 90°C

Copper Aluminum

Raceway Cable Burried in Earth Open Air

70-77°F 78-86°F 87-95°F 96-104°F 105-113°F 114-122°F 123-131°F 132-140°F 141-158°F 159-176°F

1-3 4-6 7-9 10-20 21-30 31-40 > 40

1% 2% 3% 4% 5%

Calculate Reset

Voltage - Enter the voltage at the source of the circuit. Single-phase voltages are usually 115V or 120V, while three-phase voltages are typically 208V, 230V or 480V.

Wire Size - Choose the size (AWG or kcmil) of the wire for which to calculate the maximum allowable ampacity based on the conditions chosen above in the calculator.

Phases - Select the number of phases in the circuit. This is typically single-phase or three-phase. For single-phase circuits, three wires are required. For three-phase circuits, four wires are required. One of these wires is a ground wire which can be sized down. To calculate ground wire size, use the Ground Wire Size Calculator.

Insulation - Select the thermal rating of the insulation on the wire.

Conductor - Choose the material used as a conductor in the wire. Common conductors are copper and aluminum.

Installation - Choose the installation method for the circuit. This is typically in a raceway (cable-tray or conduit), in a cable, burried in the Earth, or in open air.

Voltage Drop - Choose the maximum percentage of the source voltage drop. It is recommended not to exceed a voltage drop of 5%.

Distance - Enter the one-way length of the wires in the circuit in feet.

Note: It's recommended to check the ampacity of a wire after doing a voltage drop calculation. Always use the total length of the circuit for calculations. Consult with an engineer if your application requires more complex calculations.

Source: NFPA 70, National Electrical Code, Table 310.15(B)(16-17)