The allowable ampacity for any given wire size is not a single fixed number; it depends entirely on the insulation temperature rating and the termination limits of your equipment. The AWG wire ampacity chart below provides the exact allowable ampacities for insulated conductors rated up to 2000V, sourced directly from NEC Table 310.16 (2020/2023 editions). These values assume an ambient temperature of 30°C (86°F) and not more than three current-carrying conductors in a raceway.
The Complete AWG Wire Ampacity Chart (NEC Table 310.16)
How to read this table: Locate your wire gauge (AWG or kcmil) in the first column. Read across to the material (Copper or Aluminum) and the temperature column that matches your installation. For standard residential branch circuits using NM-B (Romex), you must use the 60°C column. For individual THHN/THWN-2 wires in conduit landing on standard breakers, use the 75°C column. The 90°C column is primarily used as the starting baseline for applying derating factors, not for final breaker sizing.
| AWG / kcmil | Copper 60°C (140°F) | Copper 75°C (167°F) | Copper 90°C (194°F) | Aluminum 75°C (167°F) | Aluminum 90°C (194°F) |
|---|---|---|---|---|---|
| 14 | 15 | 20 | 25 | - | - |
| 12 | 20 | 25 | 30 | - | - |
| 10 | 30 | 35 | 40 | - | - |
| 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 | 110 | 130 | 145 | 100 | 115 |
| 1/0 | 125 | 150 | 170 | 120 | 135 |
| 2/0 | 145 | 175 | 195 | 135 | 150 |
| 3/0 | 165 | 200 | 225 | 155 | 175 |
| 4/0 | 195 | 230 | 260 | 180 | 205 |
Values represent maximum allowable ampacities in Amperes. Refer to NFPA 70 (National Electrical Code) for complete installation conditions.
How to Read This Chart: Which Column Applies to Your Installation?
The most common mistake DIYers and junior apprentices make is looking at the 90°C column for THHN wire and assuming they can use that higher ampacity to size their breaker. You cannot. The column you must use is dictated by NEC 110.14(C) - Temperature Limitations.
- The 60°C Column: Use this for circuits rated 100A or less, or for wire sizes 14 AWG through 1 AWG, unless the equipment is specifically marked otherwise. This is the mandatory column for standard NM-B (Romex) cable, as its overall jacket is only rated to 60°C, regardless of the 90°C rating of the individual THHN conductors inside it.
- The 75°C Column: Use this for circuits rated over 100A, or for wire sizes 1/0 AWG and larger. You also use this column when using individual THHN/THWN-2 conductors in conduit that land on modern breakers and lugs explicitly marked 'AL/CU 75°C'.
- The 90°C Column: This column is almost never used for final breaker sizing because standard termination points (breakers, lugs, receptacles) are rarely rated for 90°C. Instead, the 90°C column is used as your baseline for calculating derating factors before you check the final ampacity against the 75°C or 60°C termination limits.
What the Chart Cannot Tell You: Derating and Voltage Drop
The AWG wire ampacity chart above assumes ideal conditions: an ambient temperature of exactly 30°C (86°F) and no more than three current-carrying conductors bundled together. Real-world jobsites rarely match this. Here is how derating rows modify the base value and what the table leaves out.
Ambient Temperature Correction
If your conduit runs through a hot attic in the summer, the ambient temperature might hit 50°C (122°F). According to NEC Table 310.15(B)(1), you must multiply the base ampacity by a correction factor. For 90°C THHN at 50°C ambient, the factor is 0.82. If you are running 8 AWG THHN (base 90°C ampacity = 55A), your corrected ampacity is 55 x 0.82 = 45.1A. You then verify this against your termination limits.
Conduit Fill (More Than 3 Current-Carrying Conductors)
When you pull four or more current-carrying conductors in a single raceway, they generate mutual heat. NEC Table 310.15(C)(1) requires you to apply an adjustment factor. For 4-6 conductors, you multiply the 90°C base ampacity by 80%. For 7-9 conductors, it drops to 70%. Neutral conductors that carry only the unbalanced load are not counted, but neutrals carrying harmonic loads (like in multi-wire branch circuits with non-linear loads) or switch legs do count.
Voltage Drop
The ampacity chart tells you what the wire can handle before the insulation melts; it tells you absolutely nothing about voltage drop. A 12 AWG wire on a 15A breaker is perfectly legal per the chart for a 200-foot run. However, at 15A over 200 feet on a 120V circuit, you will experience roughly a 9.5% voltage drop, leaving your load with only 108V. This will cause motors to overheat and electronics to brownout. For runs over 100 feet, always calculate voltage drop (target <3% for branch circuits) and upsize the wire accordingly, as recommended in NEC Chapter 9 informational notes.
AWG Wire Ampacity Chart FAQ
What size breaker do I use for a specific AWG wire?
For standard branch circuits, NEC 240.4(D) enforces strict upper limits for small conductors, regardless of the ampacity chart. You must use a maximum 15A breaker for 14 AWG, a 20A breaker for 12 AWG, and a 30A breaker for 10 AWG. For 8 AWG and larger, you size the breaker based on the ampacity chart columns (usually the 75°C column) and round down to the nearest standard breaker size (e.g., 6 AWG copper at 65A uses a 60A breaker, as 65A breakers do not exist in standard residential panels).
Does the AWG ampacity chart apply to aluminum wire?
Yes, the right side of the chart above applies to aluminum (specifically AA-8000 series alloy wire). However, aluminum has a lower ampacity per AWG size than copper and requires larger physical wire for the same current. Furthermore, aluminum must only be terminated on devices explicitly marked 'CO/ALR' or 'AL/CU', and the terminals must be treated with an antioxidant compound like Noalox to prevent galvanic corrosion and thermal creep, which can cause loose connections and fires over time.
Why is my wire ampacity lower than the 90°C column?
Because of the 'weakest link' rule in NEC 110.14(C). Even if your THHN wire insulation can withstand 90°C, the brass or tin-plated aluminum lug inside your circuit breaker, panelboard, or receptacle is typically only rated for 75°C. If you push 90°C heat into a 75°C terminal, the terminal will degrade, lose spring tension, and eventually arc. Therefore, your final allowable ampacity is capped by the lowest temperature rating of any component in the circuit, which is almost always 75°C or 60°C.
Can I use the 90°C column for derating calculations?
Yes, and you should. This is the primary purpose of the 90°C column in modern wiring. If you have 4 current-carrying 10 AWG THHN wires in a conduit, you start with the 90°C base ampacity of 40A. You apply the 80% derating factor (40A x 0.80 = 32A). Because 32A is still greater than the 75°C termination limit of 35A (wait, 10 AWG 75°C is 35A, so 32A is less, meaning the derated wire is now limited to 32A). You then protect this wire with a 30A breaker. The 90°C column gives you a 'thermal buffer' to absorb derating penalties without having to upsize the physical wire gauge.
