The most common house wire sizes for standard 120V and 240V branch circuits are 14 AWG (15 amps), 12 AWG (20 amps), and 10 AWG (30 amps). However, when sizing feeders for subpanels, electric vehicle chargers, or heavy appliances, you must reference the official ampacity tables. This guide provides the complete house wire size chart for copper conductors, directly aligned with the National Electrical Code (NEC) standards.
The Complete House Wire Size Chart (NEC Table 310.16)
The table below details the allowable ampacities for insulated copper conductors rated up to 2000 volts. Assumptions: This data assumes copper conductors (THHN, THWN-2, XHHW) in an ambient temperature of 30°C (86°F) with not more than three current-carrying conductors in a single raceway or cable.
| AWG / kcmil | 60°C (140°F) | 75°C (167°F) | 90°C (194°F) | Common Residential Application |
|---|---|---|---|---|
| 14 AWG | 15A | 20A | 25A | Lighting circuits, standard receptacles (15A max breaker) |
| 12 AWG | 20A | 25A | 30A | Kitchen/bathroom small appliance circuits (20A max breaker) |
| 10 AWG | 30A | 35A | 40A | Electric dryers, window AC units (30A max breaker) |
| 8 AWG | 40A | 50A | 55A | Electric ranges, 50A EV chargers (Level 2) |
| 6 AWG | 55A | 65A | 75A | 60A subpanel feeders, tankless water heaters |
| 4 AWG | 70A | 85A | 95A | 80A-90A heavy feeders, large HVAC compressors |
| 3 AWG | 85A | 100A | 110A | 100A main service or subpanel feeders |
| 2 AWG | 95A | 115A | 130A | 100A-125A feeders (voltage drop mitigation) |
| 1 AWG | 110A | 130A | 150A | 125A subpanel feeders |
| 1/0 AWG | 125A | 150A | 170A | 150A residential service entrance |
| 2/0 AWG | 145A | 175A | 195A | 200A residential service entrance (short runs) |
| 3/0 AWG | 165A | 200A | 225A | 200A service entrance (standard for long runs) |
| 4/0 AWG | 195A | 230A | 260A | 200A service with heavy voltage drop compensation |
How to Read This Chart: Columns, Derating, and Limits
Looking up a number in the house wire size chart is only the first step. To legally and safely size your wire, you must understand how the NEC restricts the values in those columns.
Which Column Applies to Your Installation?
Under NEC 110.14(C), the ampacity of a wire is limited by the lowest temperature rating of any connected termination, conductor, or device. Most modern residential circuit breakers and receptacles are rated for 75°C. However, the NEC enforces a strict exception for small conductors: 14, 12, and 10 AWG wires must always be sized using the 60°C column for their final overcurrent protection, regardless of the insulation's 90°C rating. Furthermore, NEC 240.4(D) hard-caps the breaker size for these small wires at 15A, 20A, and 30A respectively.
How Derating Rows Modify the Base Value
The 90°C column exists primarily for derating. If you pull more than three current-carrying conductors through a single conduit, or if the ambient temperature in your attic exceeds 30°C (86°F), you must multiply the 90°C ampacity by a correction factor.
Worked Example: You are pulling four current-carrying 10 AWG THHN wires through a conduit to a detached garage. According to NEC Chapter 9, Table 310.15(C)(1), four conductors require an 80% derating factor. You look at the 90°C column for 10 AWG (40A) and multiply by 0.80, resulting in a derated ampacity of 32A. Because 32A is not a standard breaker size, you step down to the next standard size: a 30A breaker.
What the Table Cannot Tell You: Voltage Drop
This chart assumes a short wire run. It does not account for voltage drop. If you use 4 AWG copper to feed a 60A subpanel 150 feet away, the wire can safely handle the heat (ampacity), but the resistance over that distance will cause the voltage to sag below 114V under load. This sag can damage sensitive electronics and cause motors to overheat. For runs over 100 feet, always calculate voltage drop and upsize your wire by one or two AWG steps beyond what the ampacity chart demands.
Frequently Asked Questions About House Wire Sizing
What size wire do I need for a 50 amp breaker?
For a 50-amp breaker (commonly used for Level 2 EV chargers, hot tubs, or small subpanels), you must use 6 AWG copper wire. Looking at the 75°C column, 6 AWG is rated for 65A, which safely covers the 50A continuous or non-continuous load. If you are using aluminum wire (like SER cable), you must step up to 4 AWG aluminum, as aluminum has a higher resistance and lower ampacity per AWG than copper.
Can I use 14 AWG wire on a 20 amp breaker?
No. Under NEC 240.4(D), 14 AWG copper wire is strictly limited to a maximum overcurrent protective device (breaker or fuse) of 15 amps. If you wire a 20A circuit with 14 AWG, the breaker will not trip before the wire overheats and melts the insulation inside the walls. You must use 12 AWG or larger for any 20A circuit.
What wire size is required for a 100 amp subpanel feeder?
For a 100-amp subpanel, you need 3 AWG copper or 1 AWG aluminum (rated in the 75°C column). However, if the subpanel is located in a detached garage more than 100 feet away from the main panel, you should upsize to 2 AWG copper or 1/0 AWG aluminum to mitigate voltage drop. Always ensure your equipment grounding conductor is sized according to NEC Table 250.122 (an 8 AWG copper ground is required for a 100A feeder).
Does the ground wire need to be the same size as the hot wires?
No, the equipment grounding conductor (EGC) is typically smaller than the current-carrying conductors. Its only job is to carry fault current long enough to trip the breaker. For example, on a 30A circuit using 10 AWG hot wires, an 8 AWG copper ground is sufficient. On a 100A feeder using 3 AWG hot wires, an 8 AWG copper ground is also the minimum requirement. Refer to NEC Table 250.122 for exact grounding sizes based on your breaker rating.
