Wire Ampacity Chart
The Wire Ampacity Chart is a reference tool covering wire ampacity chart, wire size ampacity chart, copper wire ampacity chart, nec ampacity chart. Use the chart below to look up values instantly. Printable and downloadable versions are available on this page.
Wire Ampacity Chart — Copper Conductors
| Wire Size (AWG or kcmil) | 60°C Rating — NM-B, THHW | 75°C Rating — THW, THWN | 90°C Rating — THHN, THWN-2 | Typical Use |
|---|---|---|---|---|
| 14 AWG | 15 A | 20 A | 25 A | 15-amp circuits (NEC limits 14 AWG to 15-amp breakers) |
| 12 AWG | 20 A | 25 A | 30 A | 20-amp circuits — most common household circuit wire |
| 10 AWG | 30 A | 35 A | 40 A | 30-amp circuits — dryers, A/C, water heaters |
| 8 AWG | 40 A | 50 A | 55 A | 40 to 50-amp circuits — ranges, EV chargers |
| 6 AWG | 55 A | 65 A | 75 A | 50 to 60-amp circuits |
| 4 AWG | 70 A | 85 A | 95 A | 70-amp circuits — subpanels |
| 3 AWG | 85 A | 100 A | 110 A | 100-amp small subpanels |
| 2 AWG | 95 A | 115 A | 130 A | 100-amp service entrance |
| 1 AWG | 110 A | 130 A | 150 A | 100 to 125-amp service |
| 1/0 AWG | 125 A | 150 A | 170 A | 100 to 150-amp service |
| 2/0 AWG | 145 A | 175 A | 195 A | 150-amp service |
| 3/0 AWG | 165 A | 200 A | 225 A | 200-amp service — very common for residential main service |
| 4/0 AWG | 195 A | 230 A | 260 A | 200-amp service with margin |
| 250 kcmil | 215 A | 255 A | 290 A | 200 to 225-amp applications |
| 300 kcmil | 240 A | 285 A | 320 A | 225-amp service |
| 350 kcmil | 260 A | 310 A | 350 A | 250-amp service |
| 400 kcmil | 280 A | 335 A | 380 A | 300-amp service |
NEC ampacity values above are for conductors in free air or conduit with up to 3 current-carrying conductors at 30°C (86°F) ambient temperature. Higher conductor counts in conduit, higher ambient temperatures, and bundled cables all require derating. Always consult the full NEC tables and local codes. The 90°C column is the conductor rating — terminal ratings at devices are usually 60°C or 75°C and the lowest temperature rating in the circuit applies.
Source: National Electrical Code (NEC) 2023 Table 310.12 — NFPA 70
Aluminium Wire Ampacity Chart
| Wire Size (AWG or kcmil) | 60°C Rating (amperes) | 75°C Rating (amperes) | 90°C Rating (amperes) |
|---|---|---|---|
| 6 AWG Al | 40 A | 50 A | 55 A |
| 4 AWG Al | 55 A | 65 A | 75 A |
| 2 AWG Al | 75 A | 90 A | 100 A |
| 1/0 AWG Al | 100 A | 120 A | 135 A |
| 2/0 AWG Al | 115 A | 135 A | 150 A |
| 3/0 AWG Al | 130 A | 155 A | 175 A |
| 4/0 AWG Al | 150 A | 180 A | 205 A |
| 350 kcmil Al | 200 A | 240 A | 270 A |
Aluminium wire carries less current than the same gauge copper and requires larger wire sizes to match copper ampacity. Aluminium wiring requires anti-oxidant compound at all connections and aluminium-rated terminals. Do not connect aluminium wire to copper wire without listed AL/CU connectors.
Source: NEC 2023 Table 310.12
Common Residential Circuit Reference
| Circuit Application | Typical Amperage | Wire Size (copper) | Notes |
|---|---|---|---|
| Lighting and general outlets | 15 amps | 14 AWG | Standard bedroom, hallway, and living room circuits |
| Kitchen counter outlets and appliances | 20 amps | 12 AWG | Kitchen requires 20-amp small appliance circuits — NEC requires at least two |
| Bathroom outlets | 20 amps | 12 AWG | NEC requires GFCI protection on all bathroom circuits |
| Clothes dryer | 30 amps | 10 AWG | 4-wire circuit required for new installations (NEC 2008+) |
| Electric range or oven | 40 to 50 amps | 8 AWG | 4-wire circuit required |
| Central air conditioning | 30 to 50 amps | 10 to 8 AWG | Check equipment nameplate for exact requirements |
| Electric water heater | 30 amps | 10 AWG | Dedicated 2-pole circuit |
| EV charger Level 2 | 40 to 50 amps (for 32 to 48 amp EVSE) | 8 to 6 AWG | Size for 125% of continuous load per NEC |
| Garage and outdoor outlets | 20 amps | 12 AWG | GFCI protection required by NEC |
| Hot tub or spa | 50 to 60 amps | 6 AWG | GFCI and disconnect requirements per NEC 680 |
Source: NEC 2023 residential wiring requirements
Wire Ampacity Calculator
Enter required amps, installation type, and temperature rating to find the minimum wire gauge (AWG) for copper and aluminum, including derating for conduit fill.
Frequently Asked Questions
What size wire do I need for a 20-amp circuit?
A 20-amp circuit requires 12 AWG copper wire at the 60°C rating used for standard NM-B (Romex) cable. This is the standard wire for kitchen counter outlets, bathroom circuits, and other 20-amp applications.
What is the ampacity of 12 AWG wire?
12 AWG copper wire has an ampacity of 20 amps at the 60°C rating (standard for NM-B cable in residential construction). In conduit with THWN insulation it is rated for 25 amps at 75°C.
What gauge wire for a 30-amp circuit?
A 30-amp circuit requires 10 AWG copper wire. Common 30-amp applications include clothes dryers and electric water heaters.
What is the difference between AWG and kcmil?
AWG (American Wire Gauge) is the standard sizing system for smaller conductors — the lower the AWG number the larger the wire. Above 4/0 AWG wires are measured in kcmil (thousands of circular mils) — 250 kcmil is larger than 4/0 AWG.
Can I use 12 AWG wire on a 20-amp breaker?
Yes — 12 AWG copper wire is rated for 20 amps and is the correct wire for 20-amp circuits. 14 AWG wire must not be used on a 20-amp breaker.
Why does aluminium wire require special connections?
Aluminium expands and contracts more than copper with temperature changes — this causes connections to loosen over time leading to arcing and fire risk. All aluminium connections require anti-oxidant compound and aluminium-rated terminals marked AL/CU.
What gauge wire for a 200-amp service?
A 200-amp residential service entrance typically uses 3/0 AWG copper or 350 kcmil aluminium conductors. The exact size depends on the run length and whether the conductors are in conduit — longer runs may require upsizing.
What does AWG stand for?
AWG stands for American Wire Gauge — a standardised system for specifying conductor diameter. The gauge number is inversely related to size: 14 AWG is thinner than 12 AWG which is thinner than 10 AWG. Larger conductors above 4/0 use the kcmil system.