For standard residential branch circuits, match your breaker size to the 60°C ampacity column of NEC Table 310.16 for circuits 100A or less. A 15A lighting circuit requires 14 AWG copper wire and a 15A breaker; a 20A receptacle circuit requires 12 AWG wire and a 20A breaker. This wire and breaker size chart maps exact American Wire Gauge (AWG) sizes to their maximum allowable ampacities and standard overcurrent protection ratings, eliminating the guesswork from your next panel upgrade or subpanel feed.
How to Read This Wire and Breaker Size Chart
Before pulling wire, you must understand how the National Electrical Code (NEC) structures ampacity tables. The chart below is derived directly from NFPA 70 (NEC) Table 310.16. It lists copper conductors with common insulation types like THHN, THWN, and XHHW.
Most modern THHN wire is rated for 90°C, but you rarely get to use that full capacity. Per NEC 110.14(C), for circuits rated 100A or less (or wire sizes 14 AWG through 1 AWG), you must use the 60°C column for termination ampacity unless the breaker and equipment lugs are explicitly marked for 75°C. For circuits over 100A (or wire sizes 1/0 AWG and larger), you default to the 75°C column. The 90°C column is strictly reserved for calculating derating adjustments, which we cover below.
Complete Copper Wire and Breaker Size Chart (NEC Table 310.16)
The following spec-sheet-table provides the allowable ampacities for copper conductors in a standard 30°C (86°F) ambient environment. The 'Max Standard Breaker' column applies NEC 240.4(B) rules, mapping the wire's ampacity to the next standard overcurrent device rating (15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 125, 150, 175, 200A).
| AWG / kcmil | 60°C (140°F) Ampacity | 75°C (167°F) Ampacity | 90°C (194°F) Ampacity | Max Standard Breaker |
|---|---|---|---|---|
| 14 AWG | 15A | 20A | 25A | 15A |
| 12 AWG | 20A | 25A | 30A | 20A |
| 10 AWG | 30A | 35A | 40A | 30A |
| 8 AWG | 40A | 50A | 55A | 40A (or 50A*) |
| 6 AWG | 55A | 65A | 75A | 60A |
| 4 AWG | 70A | 85A | 95A | 70A (or 80A*) |
| 3 AWG | 85A | 100A | 115A | 100A |
| 2 AWG | 95A | 115A | 130A | 125A |
| 1 AWG | 110A | 130A | 145A | 125A (or 150A*) |
| 1/0 AWG | 125A | 150A | 170A | 150A |
| 2/0 AWG | 145A | 175A | 195A | 175A |
| 3/0 AWG | 165A | 200A | 225A | 200A |
| 4/0 AWG | 195A | 230A | 260A | 200A (or 225A*) |
*Note: NEC 240.4(B) allows rounding up to the next standard breaker size if the exact ampacity does not match a standard breaker, provided it is not over 800A. However, for dedicated branch circuits, matching the breaker to the 60°C/75°C column directly is best practice.
Decision Path: Picking Your Exact Wire and Breaker
Do not guess based on the physical thickness of the wire. Use this decision-tree-table to lock in your exact materials based on your calculated load. Remember NEC 210.20(A): if a load runs for 3 hours or more (continuous load), you must multiply the load by 1.25 to size the breaker and wire.
| Application Scenario | Max Continuous Load | Required Breaker | Exact Copper Wire Pick (60°C Col) |
|---|---|---|---|
| General Lighting & 15A Receptacles | 12A | 15A | 14 AWG (NM-B or THHN) |
| Kitchen/Dining/Bath Receptacles | 16A | 20A | 12 AWG (NM-B or THHN) |
| Electric Dryer or RV 30A Outlet | 24A | 30A | 10 AWG (THHN in conduit or 10/3 NM-B) |
| Standard Electric Range / Cooktop | 32A - 40A | 40A or 50A | 8 AWG (for 40A) or 6 AWG (for 50A) |
| Level 2 EV Charger (Hardwired) | 40A (Continuous) | 50A | 6 AWG (THHN in conduit) |
| 100A Subpanel Feeder (Short Run) | 80A - 100A | 100A | 2 AWG (Copper) or 1/0 AWG (Aluminum XHHW) |
How Derating and Bundling Modify Base Ampacity
The ampacities in the chart above assume you have no more than three current-carrying conductors in a single raceway or conduit. When you bundle multiple circuits together, the heat generated by adjacent wires cannot dissipate. This is where the 90°C column finally becomes useful.
Per NEC 310.15(C)(1), you must apply an adjustment factor to the 90°C ampacity when bundling 4 or more current-carrying conductors. The resulting derated ampacity must still be higher than the breaker rating protecting the circuit.
You are pulling four 12 AWG THHN circuits (8 current-carrying conductors total) through a single 1-inch PVC conduit to a detached garage.
- Base 90°C ampacity for 12 AWG = 30A.
- NEC Table 310.15(C)(1) for 7-9 conductors requires an 70% adjustment factor.
- 30A × 0.70 = 21A derated ampacity.
- Because 21A is greater than the 20A breaker protecting the circuit, 12 AWG THHN is legally compliant for this bundled run, even though you are using 20A breakers.
What This Chart Cannot Tell You (Voltage Drop & Local Code)
This wire and breaker size chart guarantees your wire will not melt and your breaker will trip before a fire starts. It does not guarantee your equipment will receive adequate voltage at the end of a long run. For detailed voltage drop calculations, reference resources like the U.S. Department of Energy (DOE) guidelines or specialized electrical software.
NEC Informative Annex B recommends limiting voltage drop to 3% on branch circuits and 5% on the total feeder-plus-branch system. Consider a 50A hardwired EV charger located 120 feet from the main panel. The chart above dictates 6 AWG copper wire. However, pushing 40A continuous through 120 feet of 6 AWG copper yields a voltage drop of roughly 4.8% on a 240V circuit. This exceeds the 3% branch recommendation and can cause the EV charger's internal contactors to chatter or fail prematurely. The concrete fix: Upgrade the wire to 4 AWG copper for that specific 120-foot run, while keeping the 50A breaker.
Finally, always consult Mike Holt Enterprises NEC Resources or your local Authority Having Jurisdiction (AHJ). Local amendments frequently override baseline NEC tables, particularly regarding aluminum feeder allowances, ground wire sizing (NEC 250.122), and AFCI/GFCI requirements for specific rooms. Use this chart as your baseline engineering tool, but let your local inspector's approved plans dictate the final bill of materials.
