When sizing conductors for residential or commercial branch circuits, the direct answer for standard copper wire ampacities is as follows: 14 AWG is rated for 15A, 12 AWG for 20A, 10 AWG for 30A, 8 AWG for 40A, 6 AWG for 55A, and 4 AWG for 70A. These values assume standard installation conditions and are derived from the 60°C column of the National Electrical Code (NEC). While frequently searched as a 'guage wire chart', the correct technical term is gauge (or American Wire Gauge, AWG). The chart below provides the complete, data-dense reference you need to size conductors safely and legally.

Quick-Jump Bookmark Rows: For 95% of residential DIY and trade work, you only need to memorize five rows: 14 AWG (15A lighting/outlets), 12 AWG (20A kitchen/bath appliances), 10 AWG (30A dryers/water heaters), 8 AWG (40A ranges/cooktops), and 6 AWG (55A/60A subpanels and EV chargers).

The Master AWG Gauge Wire Chart (NEC Table 310.16)

How to read this table: This data is sourced directly from NFPA 70 (National Electrical Code) Table 310.16 for copper conductors. The three temperature columns (60°C, 75°C, 90°C) represent the maximum allowable ampacity based on the lowest temperature rating of any connected device, termination, or conductor insulation in the circuit. The values assume an ambient temperature of 30°C (86°F) and not more than three current-carrying conductors in a raceway. If your installation deviates from these baseline assumptions, you must apply derating factors (covered in the final section).

AWG Size 60°C (140°F)
NM-B / 100A or less		 75°C (167°F)
THHN / Over 100A		 90°C (194°F)
Derating Only		 Common Residential Application
14 AWG15A20A25A15A Lighting & Receptacle Circuits
12 AWG20A25A30A20A Kitchen, Bath, & Garage Outlets
10 AWG30A35A40A30A Water Heaters, Window ACs
8 AWG40A50A55A40A/50A Ranges, Cooktops, EVSE
6 AWG55A65A75A60A Subpanels, Heavy EV Chargers
4 AWG70A85A95A85A Large Subpanels, Service Entrances
3 AWG85A100A115A100A Subpanel Feeders
2 AWG95A115A130A100A/125A Service Entrance Feeders
1 AWG110A130A145A150A Subpanel Feeders
1/0 AWG125A150A170A150A/200A Service Entrance
2/0 AWG145A175A195A200A Residential Service Entrance
3/0 AWG165A200A225A200A/225A Heavy Commercial Service
4/0 AWG195A230A260A200A/250A Large Residential Service

Which Ampacity Column Applies to Your Installation?

The most common mistake DIYers and junior apprentices make is looking at the 90°C column because it offers the highest ampacity, then sizing their breaker based on that number. This is a direct code violation and a fire hazard. Here is how to determine which column dictates your final breaker size, governed by NEC Section 110.14(C).

The 60°C Column: The Default for Residential Branch Circuits

For any circuit rated 100 amps or less, you must use the 60°C column to determine your final breaker size, unless the equipment is specifically listed and identified for use with 75°C conductors. Furthermore, standard residential non-metallic sheathed cable (NM-B, commonly known by the brand name Romex) has an insulation rating strictly limited to 60°C. Even if you pull individual THHN wires in conduit to a receptacle, the receptacle terminals are typically rated for 60°C. Therefore, a 12 AWG NM-B cable is capped at 20A, and a 10 AWG NM-B cable is capped at 30A, regardless of the breaker size.

The 75°C Column: Feeders and Heavy Equipment

You may use the 75°C column for circuits rated over 100 amps, or for circuits 100A and under if both the wire insulation (like THHN/THWN-2) and the equipment terminations (like a main breaker lug or a heavy-duty contactor) are explicitly rated for 75°C. This is the column you will use when sizing aluminum or copper feeders for subpanels, as most modern panelboard lugs are rated for 75°C.

The 90°C Column: Derating Calculations Only

The 90°C column is never used to determine the final ampacity for breaker sizing in standard terminations. It exists solely as a starting point for derating calculations. If you have to apply a temperature or bundling derating factor, you apply that percentage to the 90°C base value, and then compare the result to the 60°C or 75°C column. The final allowable ampacity is the lower of the two numbers.

Safety Caveat: Always verify the terminal temperature rating on the equipment nameplate or manufacturer datasheet. If a 60A disconnect switch has terminals rated only for 60°C, you must use the 60°C column for your wire sizing, even if you are using 90°C THHN wire in the conduit.

Derating, Voltage Drop, and What the Chart Cannot Tell You

The gauge wire chart above assumes perfect, baseline conditions: an ambient air temperature of 30°C (86°F) and no more than three current-carrying conductors bundled together in a single raceway or conduit. When real-world jobsite conditions deviate from this, the chart's base values become dangerously optimistic.

How Derating Modifies the Base Value

When you pull more than three current-carrying conductors (CCCs) through a single conduit, the wires heat each other up. NEC Table 310.15(C)(1) requires you to 'derate' the ampacity. Note that grounding wires (equipment grounding conductors) do not count as CCCs, but neutral wires in multi-wire branch circuits or 3-phase systems often do.

Worked Numeric Example:
You are pulling four 10 AWG THHN current-carrying conductors through a single EMT conduit to feed two 240V circuits.

  1. Look at the 90°C column for 10 AWG: 40A.
  2. Check the derating table for 4-6 conductors: The adjustment factor is 80%.
  3. Multiply: 40A × 0.80 = 32A.
  4. Now, compare 32A to the standard termination column (60°C for 10 AWG, which is 30A).
  5. The final allowable ampacity is the lower number: 30A. You must protect this wire with a maximum 30A breaker.
If you had pulled six CCCs in that same conduit, the derating factor drops to 50%. 40A × 0.50 = 20A. Your 10 AWG wire is now legally limited to 20A, and you would need to upsize to 8 AWG to maintain a 30A circuit.

What the Chart Cannot Tell You: Voltage Drop

NEC Table 310.16 tells you the maximum current a wire can carry before the insulation melts or the breaker trips. It tells you absolutely nothing about voltage drop. A 12 AWG wire is legally rated for 20A at 150 feet, but at that distance, the resistance of the copper will cause a voltage drop exceeding the NEC's recommended 3% limit for branch circuits. Your 120V outlet will read 112V under load, which can cause motors to overheat and electronics to brown out.

As a rule of thumb for 120V circuits: if your one-way wire run exceeds 50 feet on a 15A circuit (14 AWG) or 75 feet on a 20A circuit (12 AWG), you must upsize the wire gauge by one step to compensate for voltage drop, regardless of what the ampacity chart permits. For 240V circuits, you generally have twice the distance before voltage drop becomes a factor. Always calculate voltage drop for runs over 100 feet using the formula: VD = (2 × L × I × R) / 1000, where L is length in feet, I is current in amps, and R is the resistance per 1000 feet from NEC Chapter 9, Table 8.

Finally, remember that local authorities having jurisdiction (AHJ) and specific utility requirements always supersede general reference charts. Use this gauge wire chart as your baseline planning tool, but always verify your final design against local code amendments and the specific equipment installation manuals.