If you are sizing branch circuits or feeders, here is the direct answer for the most common residential copper wire sizes: 14 AWG is rated for 15 amps, 12 AWG is rated for 20 amps, 10 AWG is rated for 30 amps, 8 AWG is rated for 40 or 50 amps, and 6 AWG is rated for 55 or 65 amps. The exact ampacity depends entirely on the temperature rating of your termination points, not just the wire insulation.
Safety Warning: Any work involving mains voltage (>50V AC) requires de-energizing the panel, locking out the breaker, and verifying the circuit is dead with a tested multimeter. Local codes may require a licensed electrician for feeder and subpanel work. The guidance below reflects NEC-style practice; your local Authority Having Jurisdiction (AHJ) has final authority.
How to Read the AWG Wire Chart (And Which Column Applies)
The most common mistake DIYers and junior electricians make is looking at the wire's insulation rating and ignoring the termination rating. A spool of THHN wire is rated for 90°C, but that does not mean you can use the 90°C ampacity column for your final breaker sizing.
To read the NFPA 70 National Electrical Code (NEC) ampacity tables correctly, you must follow NEC 110.14(C), which governs termination provisions:
- The 60°C Column (TW, UF): You must use this column for circuits rated 100 amps or less, unless the equipment (breaker, receptacle, or lug) is explicitly marked for 75°C. Most standard 15A and 20A residential receptacles fall here.
- The 75°C Column (THW, THWN, SE): Use this column for circuits over 100 amps, or for circuits 100A and under if the equipment is specifically marked "75°C" or "AL/CU" (which implies a 75°C rating for copper). Most modern main breakers and subpanel lugs are rated 75°C.
- The 90°C Column (THHN, THWN-2, XHHW): This column is almost never used for final ampacity sizing. It is strictly used as the starting base value for applying ambient temperature and bundling derating factors.
The Master AWG Wire Chart (NEC Table 310.16)
The table below covers standard copper conductor sizes from 14 AWG up to 4/0 AWG. It assumes an ambient temperature of 30°C (86°F) and not more than three current-carrying conductors in a raceway or cable.
| AWG Size | 60°C Column (TW, UF-B) |
75°C Column (THW, THWN, SE) |
90°C Column (THHN, THWN-2) |
|---|---|---|---|
| 14 AWG | 15A | 20A | 25A |
| 12 AWG | 20A | 25A | 30A |
| 10 AWG | 30A | 35A | 40A |
| 8 AWG | 40A | 50A | 55A |
| 6 AWG | 55A | 65A | 75A |
| 4 AWG | 70A | 85A | 95A |
| 3 AWG | 85A | 100A | 110A |
| 2 AWG | 95A | 115A | 130A |
| 1 AWG | 110A | 130A | 145A |
| 1/0 AWG | 125A | 150A | 170A |
| 2/0 AWG | 145A | 175A | 195A |
| 3/0 AWG | 165A | 200A | 225A |
| 4/0 AWG | 195A | 230A | 260A |
Derating and What the Chart Cannot Tell You
The baseline numbers in the chart above assume ideal conditions. In the real world, you must adjust for heat accumulation using derating factors.
How Derating Modifies the Base Value
When you pull more than three current-carrying conductors through a single conduit, the wires heat each other up. NEC Table 310.15(C)(1) requires you to multiply the wire's ampacity by a correction factor. Crucially, you always apply derating factors to the 90°C column base value.
For example, if you pull four 10 AWG THHN (90°C) current-carrying conductors in a conduit to feed a multi-wire branch circuit or a smart switch setup:
- Base 90°C ampacity for 10 AWG = 40A.
- Derating factor for 4-6 conductors = 80%.
- Derated ampacity = 40A × 0.80 = 32A.
- You can still protect this wire with a 30A breaker. However, if you had six conductors (derating to 70%), the math becomes 40A × 0.70 = 28A, forcing you to drop to a 25A breaker or upsize to 8 AWG wire.
What the Table Cannot Tell You
The AWG ampacity chart only dictates thermal limits (preventing the insulation from melting or catching fire). It completely ignores voltage drop. If you are running a 12 AWG wire to a shed 200 feet away, the chart says it can safely carry 20A thermally, but the resistance of 400 feet of total conductor (hot and neutral) will cause a massive voltage drop, potentially damaging motors or tripping breakers. For runs over 100 feet, always calculate voltage drop and expect to upsize your wire by one or two AWG steps.
AWG Wire Chart FAQ
What size wire do I need for a 50-amp breaker?
For a 50-amp breaker using copper wire, you need 6 AWG if your termination points (breaker and receptacle lugs) are rated for 75°C, which is standard for 50A equipment. If you are using aluminum wire (like SER cable for a feeder), you must upsize to 4 AWG aluminum, as the 75°C column for 4 AWG aluminum is exactly 55A. Never use 8 AWG copper for a 50A breaker; its 75°C rating is only 50A, and NEC rules generally prohibit sizing a wire exactly at the breaker limit for continuous loads.
Can I use the 90°C column for my home wiring terminations?
Almost never. While the wire in the walls (like THHN/THWN-2 in conduit or Romex NM-B) might have 90°C rated insulation, the breakers, lugs, and receptacles are typically rated for 60°C or 75°C. NEC 110.14(C) mandates that the lowest temperature rating in the circuit dictates the final ampacity. You only use the 90°C column as a mathematical starting point before applying bundling or ambient temperature derating factors.
How does voltage drop change my AWG wire chart selection?
Voltage drop is a function of distance, current, and wire resistance, none of which are captured in the standard ampacity chart. The NEC recommends keeping voltage drop under 3% for branch circuits and 5% overall. As a practical rule of thumb: if your 120V circuit run exceeds 50 feet at max load, or your 240V run exceeds 100 feet, run a voltage drop calculator. You will frequently find that a 30A circuit requiring 10 AWG thermally will need 8 AWG or even 6 AWG to maintain acceptable voltage at the far end of a long driveway or detached garage.
What is the difference between AWG and kcmil on the wire chart?
AWG (American Wire Gauge) is used for smaller wire sizes, maxing out at 4/0 AWG (which is roughly 211,600 circular mils). Once you need conductors larger than 4/0 AWG for heavy commercial feeders or massive residential services (like 320A or 400A residential splits), the chart transitions to kcmil (thousands of circular mils). The next standard size up from 4/0 AWG is 250 kcmil, followed by 300 kcmil, 350 kcmil, and so on. Kcmil measures the actual cross-sectional area of the conductor rather than using the inverse logarithmic gauge scale.
