If you need the direct answer for standard residential branch circuits right now: use 14 AWG for 15-amp circuits, 12 AWG for 20-amp circuits, and 10 AWG for 30-amp circuits. Whether you searched for a 'wire gauge chart' or the common search typo 'wire gague chart', the physics and the National Electrical Code (NEC) remain exactly the same. Sizing wire correctly is about matching the conductor's ampacity to the overcurrent protective device (the breaker) while accounting for insulation temperature limits.
Below is the definitive reference for copper wire ampacity, built directly from NEC Table 310.16 (formerly 310.15(B)(16)). Bookmark this page, use the quick-jump rows for your specific breaker size, and follow the decision tree to lock in your final material pick.
How to Read the NEC Wire Gauge Chart (Table 310.16)
The most common mistake DIYers and junior apprentices make is looking at the highest temperature column and assuming that is the wire's legal ampacity. To read this chart correctly, you must understand which column applies to your specific installation.
- 60°C Column: By law (NEC 240.4(D)), circuits rated 100A or less using 14, 12, or 10 AWG wire must use the 60°C ampacity column for overcurrent protection, even if the wire insulation is rated for 90°C. This is because standard residential breakers and receptacles are typically tested and rated for 60°C terminations.
- 75°C Column: Used for larger conductors (8 AWG and larger) where the termination equipment (like a main panel lug or a heavy-duty disconnect) is explicitly rated for 75°C.
- 90°C Column: You rarely use this column to determine your final breaker size. Instead, this column is used as your starting point for calculating derating factors (like bundling wires in a hot attic) before you apply the final terminal temperature limits.
For a deeper dive into the exact code language governing these temperature limitations, refer to the National Fire Protection Association's NEC guidelines.
The Master Wire Gauge & Ampacity Chart (Copper)
The following data is extracted from NEC Table 310.16 for Copper conductors with common residential insulations (THHN, THWN-2, XHHW). Use the quick-jump highlights to find the most queried residential breaker sizes.
| AWG / kcmil | 60°C (140°F) Terminals & Small Wire |
75°C (167°F) Standard Equipment |
90°C (194°F) Derating Starting Point |
|---|---|---|---|
| 14 AWG (15A Breaker) | 15 Amps | 20 Amps | 25 Amps |
| 12 AWG (20A Breaker) | 20 Amps | 25 Amps | 30 Amps |
| 10 AWG (30A Breaker) | 30 Amps | 35 Amps | 40 Amps |
| 8 AWG | 40 Amps | 50 Amps | 55 Amps |
| 6 AWG (50A-60A Breaker) | 55 Amps | 65 Amps | 75 Amps |
| 4 AWG | 70 Amps | 85 Amps | 95 Amps |
| 3 AWG | 85 Amps | 100 Amps | 115 Amps |
| 2 AWG (100A Subpanel) | 95 Amps | 115 Amps | 130 Amps |
| 1 AWG | 110 Amps | 130 Amps | 145 Amps |
| 1/0 AWG | 125 Amps | 150 Amps | 170 Amps |
| 2/0 AWG | 145 Amps | 175 Amps | 195 Amps |
| 3/0 AWG | 165 Amps | 200 Amps | 225 Amps |
| 4/0 AWG (200A Service) | 195 Amps | 230 Amps | 260 Amps |
Derating: When the Chart's Base Value Drops
The ampacity values in the table above assume two things: an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors bundled together in a single raceway or conduit. When you violate either of those assumptions, you must apply derating factors, which modify the base value.
1. Bundling (More Than 3 Current-Carrying Conductors)
When you pull multiple circuits through a single conduit, the wires heat each other up. Per NEC Table 310.15(C)(1), if you have 4 to 6 current-carrying conductors in a conduit, you must multiply the 90°C column ampacity by 80%.
Worked Example: You are pulling four 12 AWG THHN wires (two hot, two neutral for two separate 20A circuits) through one EMT conduit. The 90°C ampacity for 12 AWG is 30A. Multiplying 30A by 0.80 gives you a derated ampacity of 24A. Because 24A is still greater than your 20A breaker, the 12 AWG wire is legally compliant. However, if you pulled nine conductors (50% derating), your 12 AWG wire would drop to 15A, forcing you to upsize to 10 AWG to maintain a 20A circuit.
2. Ambient Temperature Corrections
If you run wire through an attic that reaches 120°F (49°C) in the summer, you must apply a temperature correction factor. For 90°C wire in a 46-50°C ambient environment, you multiply the 90°C ampacity by 0.82. Always calculate the derated ampacity first, then verify it against the terminal temperature limits (60°C or 75°C) for your final breaker sizing. For comprehensive examples on bundling and temperature corrections, Electrical 101's wire sizing guide provides excellent visual breakdowns.
Decision Tree: Picking the Exact Wire for Your Circuit
Stop guessing. Use this decision-tree-table to terminate your planning phase with one concrete material pick.
| Scenario / Load Requirement | Conductor Type | NEC Column Used | Final Concrete Pick |
|---|---|---|---|
| Standard 15A Lighting / Receptacle Circuit | Copper NM-B (Romex) | 60°C (per 240.4(D)) | 14 AWG Copper |
| Standard 20A Kitchen/Bathroom/Garage Receptacles | Copper THHN in Conduit | 60°C (per 240.4(D)) | 12 AWG Copper |
| 30A Dryer or RV Receptacle (120/240V) | Copper NM-B or THHN | 60°C (per 240.4(D)) | 10 AWG Copper |
| 50A Electric Range or Hot Tub (Short Run) | Copper THHN in Conduit | 75°C (Equipment rated 75°C) | 6 AWG Copper |
| 60A Subpanel Feeder (Short Run, < 50ft) | Copper THHN or XHHW | 75°C (Equipment rated 75°C) | 4 AWG Copper |
| General Purpose Branch Circuits (The 'Catch-All') | Copper THHN | 60°C Limit / 90°C Derating | DEFAULT PICK: 12 AWG Copper |
What This Wire Gauge Chart Cannot Tell You
While NEC Table 310.16 is the undisputed authority on ampacity (the ability of a wire to carry current without melting its insulation), it is blind to three critical real-world factors. If you ignore these, your code-compliant wire will still perform poorly.
- Voltage Drop Over Distance: The chart assumes a short run. If you are wiring a detached garage 150 feet away from your main panel, 10 AWG wire on a 30A circuit will experience severe voltage drop, causing motors to overheat and lights to dim. As a rule of thumb, limit voltage drop to 3% for branch circuits and 5% for the total feeder-plus-branch run. For long runs, you must upsize the wire (e.g., jumping from 10 AWG to 8 AWG or 6 AWG) purely to maintain voltage, even if the breaker size remains 30A.
- Conduit Fill Capacity: You might calculate that six 12 AWG wires are perfectly legal for your derating scenario, but physically fitting six 12 AWG THHN wires plus a ground wire into a 1/2-inch EMT conduit violates NEC Chapter 9 conduit fill tables. You will need to upsize the conduit or use fewer wires per pipe.
- Short-Circuit Withstand Ratings: Ampacity handles continuous heat. It does not tell you if the wire can survive the massive magnetic and thermal forces of a 10,000-amp short circuit before the breaker trips. This is why proper breaker coordination and equipment AIC (Ampere Interrupting Capacity) ratings are just as vital as wire sizing.
The Final Verdict: If you are wiring standard residential branch circuits and want a single, foolproof baseline that handles 20A loads, survives minor bundling derating, and keeps voltage drop manageable on runs up to 75 feet, buy 12 AWG Copper THHN/THWN-2 (or 12/2 NM-B for exposed stud cavities) and protect it with a 20A breaker. It is the most versatile, code-compliant workhorse in the residential electrician's toolkit.
