Ampacity Charts | Wire Gauge Chart
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Wire Size & Amp Ratings
| Copper | Aluminum | ||||
|---|---|---|---|---|---|
| Wire Gauge Size | 60°C (140°F) NM-B, UF-B | 75°C (167°F) THW, THWN, SE, USE, XHHW | 90°C (194°F) THWN-2, THHN, XHHW-2, USE-2 | 75°C (167°F) THW, THWN, SE, USE, XHHW | 90°C (194°F) XHHW-2, THHN, THWN-2 |
| 14 | 15 | 20 | 25 | --- | --- |
| 12 | 20 | 25 | 30 | 20 | 25 |
| 10 | 30 | 35 | 40 | 30 | 35 |
| 8 | 40 | 50 | 55 | 40 | 45 |
| 6 | 55 | 65 | 75 | 50 | 55 |
| 4 | 70 | 85 | 95 | 65 | 75 |
| 3 | 85 | 100 | 115 | 75 | 85 |
| 2 | 95 | 115 | 130 | 90 | 100 |
| 1 | --- | 130 | 145 | 100 | 115 |
| 1/0 | --- | 150 | 170 | 120 | 135 |
| 2/0 | --- | 175 | 195 | 135 | 150 |
| 3/0 | --- | 200 | 225 | 155 | 175 |
| 4/0 | --- | 230 | 260 | 180 | 205 |
| 250 | --- | 255 | 290 | 205 | 230 |
| 300 | --- | 285 | 320 | 230 | 260 |
| 350 | --- | 310 | 350 | 250 | 280 |
| 500 | --- | 380 | 430 | 310 | 350 |
| 600 | --- | 420 | 475 | 340 | 385 |
| 750 | --- | 475 | 535 | 385 | 435 |
| 1000 | --- | 545 | 615 | 445 | 500 |
Download Ampacity Chart PDF:
- Understanding Ampacity: Ampacity refers to the maximum safe current a conductor can carry continuously under specific operating conditions without exceeding its designated temperature limit. Current is measured in amperes (amps). Selecting the appropriate wire size for a circuit is crucial to prevent overheating, which can lead to damage and fire hazards.
- Devices and Amp Draw: The number and type of electrical devices connected to a circuit determine the ampacity requirement of the conductor. For example, a typical general-purpose household circuit is designed for a maximum current of 20 amps, while lighting circuits may be limited to 15 amps.
- Calculating Ampacity Needs: To calculate the load requirement for a circuit, first add up the wattages of all devices planned for the circuit. Divide the total wattage by the system voltage (typically 120V or 240V). This calculation gives you the required current (amps). You may also need to consider voltage drop or derating requirements before making a final determination of the proper conductor size.
Ampacity Calculator
Simplify complex wire ampacity calculations with Cerrowire’s convenient Online Ampacity Calculator. This intuitive calculator takes the guesswork out of electrical code compliance, ensuring you select the right conductor size for your specific application.
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WARNING! Installation of electrical wire can be hazardous and, if done improperly can result in personal injury or property damage. For safe wiring practices, consult the National Electrical Code®, your local building inspector, or a qualified electrician.
Ampacities are based on the 2017 NEC and do not reflect any temperature correction or ampacity adjustments that may be required. Please consult a qualified electrician or professional engineer to determine the appropriate values for your specific application.