If you are looking for the standard wire current chart used in the United States, you need NEC Table 310.16 (formerly 310.15(B)(16)). For standard residential copper branch circuits, the quick-jump baseline values are: 14 AWG = 15A, 12 AWG = 20A, 10 AWG = 30A, 8 AWG = 40A, and 6 AWG = 55A. However, simply matching the breaker size to the 60°C column is only the first step. Real-world ampacity depends on insulation type, termination ratings, and conduit fill.
How to Read the NEC Wire Current Chart
The wire current chart is not a single list of numbers; it is a matrix divided by insulation temperature ratings. According to the NFPA 70 National Electrical Code (NEC), the three primary columns for copper conductors are 60°C (140°F), 75°C (167°F), and 90°C (194°F). Knowing which column applies to your specific installation is the most common point of failure for DIYers and junior apprentices.
Which column applies to you?
- 60°C Column: Mandatory for NM-B (Romex) cable assemblies per NEC 334.80, regardless of the 90°C rating of the individual THHN wires inside the sheath. Also applies to circuits rated 100A or less where equipment temperature ratings are unmarked.
- 75°C Column: Used for THHN/THWN-2 wires in conduit terminating on modern, marked 75°C lugs, and for circuits over 100A.
- 90°C Column: Almost never used for final ampacity selection. Its primary legal use is as the base value for calculating derating factors (ambient temperature and conduit bundling).
Complete Copper Wire Current Chart (NEC Table 310.16)
The table below covers the most queried AWG sizes for residential and light commercial copper conductors (THHN, THWN-2, XHHW). Source: NFPA 70 (NEC) Table 310.16, 75°C and 90°C wet/dry locations.
| Wire Size (AWG/kcmil) | 60°C (140°F) - NM-B / Old Equip. | 75°C (167°F) - THHN in Conduit | 90°C (194°F) - Derating Base |
|---|---|---|---|
| 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 |
* Note: Per NEC 240.4(D), small conductors (14, 12, and 10 AWG) have strict overcurrent protection limits of 15A, 20A, and 30A respectively, even if the 75°C or 90°C columns show higher ampacities.
Bookmark Quick-Jump Rows:
- Standard 15A Receptacle Circuit: 14 AWG NM-B (60°C column = 15A).
- Standard 20A Kitchen/Bath Circuit: 12 AWG NM-B (60°C column = 20A).
- 30A Dryer / RV Receptacle: 10 AWG (60°C column = 30A).
- 50A Range / Hot Tub Feeder: 6 AWG Copper (75°C column = 65A, protected at 50A).
- 100A Subpanel Feeder: 3 AWG Copper (75°C column = 100A) or 2 AWG for voltage drop buffer.
- 200A Service Entrance: 2/0 AWG Copper (75°C column = 175A, allowed for 200A residential service per 310.12) or 4/0 AWG for standard rounding.
Derating and Edge Cases: What the Chart Cannot Tell You
The wire current chart assumes ideal conditions: an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors in a raceway. When real-world conditions deviate, you must apply derating factors to the 90°C column, then compare the result to your termination limits.
1. Conduit Bundling (NEC 310.15(C)(1))
When you pull four to six current-carrying conductors in a single conduit, the wires heat each other up. You must multiply the 90°C base ampacity by 80%. Example: You are pulling four 12 AWG THHN wires (two hots, one neutral, one ground; the ground does not count). The 90°C base is 30A. Multiplying 30A by 0.80 yields 24A. Because 24A is still greater than your 20A breaker, the 12 AWG wire is legally compliant.
2. Ambient Temperature (NEC 310.15(B)(1))
If your conduit runs through an attic that reaches 110°F (43°C), you must apply a temperature correction factor. For 90°C insulation at 41-45°C ambient, the multiplier is 0.87. A 6 AWG THHN wire (90°C base = 75A) drops to 65.25A.
What the Table Cannot Tell You:
- Voltage Drop: Table 310.16 only prevents the wire from melting. It does not guarantee your equipment will run. For long runs (e.g., a detached garage 150 feet away), a 6 AWG wire might handle the 50A thermally, but the voltage drop could exceed the recommended 3% limit for branch circuits. Always calculate voltage drop for runs over 50 feet.
- Physical Lug Fit: A 4/0 AWG wire might be rated for 230A, but it may not physically bend into the small lug of a standard 100A breaker. You may need to use a larger wire with a higher temperature rating or a pigtail.
- Short-Circuit Withstand: The chart dictates steady-state thermal limits. It does not tell you if the wire can survive the magnetic and thermal forces of a 10,000A short-circuit event before the breaker trips. That requires I²t let-through calculations.
Wire Current Chart FAQ
What size wire do I need for a 50 amp breaker?
For a standard 50A circuit (like a welder or EV charger), you need 6 AWG copper wire if you are using THHN in conduit and terminating on 75°C rated lugs (6 AWG at 75°C = 65A). If you are using NM-B (Romex) cable, you are forced to use the 60°C column, where 6 AWG is only rated for 55A. While 55A is technically above 50A, many inspectors prefer 4 AWG copper for NM-B to provide a safety margin and account for voltage drop. Furthermore, if the 50A load is considered 'continuous' (running for 3 hours or more, like an EV charger), NEC 210.20(A) requires the breaker and wire to be sized at 125% of the load (62.5A), mandating 4 AWG copper regardless of insulation type.
Can I use the 90°C column for my breaker terminations?
Almost never. Under NEC 110.14(C), the ampacity of a circuit is limited by the lowest temperature rating of any connected device, termination, or conductor. While THHN wire is rated for 90°C, standard residential breakers (Square D Homeline, Siemens, Eaton BR) and receptacles are typically only tested and rated for 75°C terminations. You use the 90°C column exclusively as a starting point to calculate derating penalties for heat and bundling. Once derated, the final ampacity must still meet the 75°C (or 60°C) termination requirements.
How does bundling wires in a conduit change the wire current chart?
When you bundle more than three current-carrying conductors in a single raceway or conduit, the heat dissipation of the wires is compromised. You must apply a derating multiplier to the 90°C column ampacity. For 4-6 conductors, multiply by 80%. For 7-9 conductors, multiply by 70%. For 10-20 conductors, multiply by 50%. Note that equipment grounding wires (bare copper or green) do not count as current-carrying, but neutrals on multi-wire branch circuits or non-linear loads (like LED drivers) do count.
Does this wire current chart apply to aluminum wire?
No. The table provided above is strictly for copper conductors. Aluminum has a higher electrical resistance and requires a larger cross-sectional area to carry the same current safely. For example, to carry 100A at 75°C, copper requires 3 AWG, but aluminum requires 1 AWG. If you are sizing aluminum feeders (common for service entrances and subpanels due to cost savings), you must reference the aluminum section of NEC Table 310.16. Additionally, aluminum terminations require specific anti-oxidant compound (like Noalox) and precise torque settings to prevent thermal runaway at the lugs.
