If you are sizing aluminium wire for a feeder or service entrance, here are the direct answers for the most common residential loads based on the 75°C column of NEC Table 310.16: Use 1 AWG AL for a 100-amp subpanel, 4/0 AWG AL for a 200-amp residential service, and 250 kcmil AL for a 200-amp non-dwelling (commercial) service. Never use 2 AWG AL for a 100-amp breaker; its 75°C ampacity is only 90 amps, which violates the next-size-up rule since 100A is a standard breaker size.

This aluminium wire gauge chart provides the exact ampacities you need, but picking the right row requires understanding terminal temperature limits, ambient derating, and dwelling-specific exceptions. Below is the complete reference data and the decision path to lock in your exact wire size.

How to Read This Aluminium Wire Gauge Chart

The chart below contains three temperature columns: 60°C, 75°C, and 90°C. These columns represent the thermal limits of the wire's insulation (like XHHW-2 or THHN) and the equipment terminations it connects to. Here is how to select the correct column for your installation:

The 75°C Default Rule (NEC 110.14(C)): Modern breakers and lugs are generally rated for 75°C. However, NEC 110.14(C)(1)(a) mandates that for circuits rated 100 amps or less, you must use the 60°C column unless the equipment is explicitly marked otherwise. For circuits over 100 amps, you default to the 75°C column. The 90°C column is almost never used for final ampacity; it is only used as a starting point for derating calculations.

When reading the rows, note that aluminium wire is restricted by NEC 310.106 to 8 AWG or larger for general branch circuit wiring. You will not find 14, 12, or 10 AWG aluminium in standard building wire tables because those sizes are exclusively copper in modern residential branch circuits.

Complete Aluminium Wire Ampacity Chart (NEC Table 310.16)

The following table lists the allowable ampacities for insulated aluminium conductors rated up to 2000 volts, assuming an ambient temperature of 30°C (86°F) and not more than three current-carrying conductors in a raceway. Data sourced from the Cerro Wire NEC Ampacity Charts and NFPA 70.

Wire Size (AWG/kcmil) 60°C Column (≤100A Default) 75°C Column (>100A Default) 90°C Column (Derating Start)
8 AWG30A40A45A
6 AWG40A50A55A
4 AWG55A65A75A
3 AWG65A75A85A
2 AWG75A90A100A
1 AWG85A100A115A
1/0 AWG100A120A135A
2/0 AWG115A135A150A
3/0 AWG130A155A170A
4/0 AWG150A180A205A
250 kcmil170A205A235A
300 kcmil190A240A260A
350 kcmil210A260A290A
400 kcmil225A280A315A

Derating Factors: When the Base Chart Isn't Enough

The ampacities above assume perfect conditions: 30°C (86°F) ambient temperature and a maximum of three current-carrying conductors in a conduit. If your installation deviates, you must apply derating factors to the 90°C column, then compare the result to the termination column limit. The final allowable ampacity is the lower of the two numbers.

Ambient Temperature Correction

If you are running aluminium feeder wire through a hot attic in the summer, the ambient temperature easily exceeds 30°C. According to NEC Table 310.15(B)(1), if the attic reaches 45°C (113°F), you must multiply the 90°C base ampacity by 0.87.

  • Example: You are pulling 4/0 AWG AL for a 150A subpanel through a hot attic. The 90°C base is 205A. Multiply 205A × 0.87 = 178.35A. Because 178.35A is greater than the 75°C termination limit of 180A, the wire is still legally rated for 180A at the lugs, safely covering your 150A load.

Conductor Bundling (More Than 3 Current-Carrying Conductors)

If you pull two 240V circuits (4 hot wires) in the same PVC conduit, the wires heat each other up. NEC Table 310.15(C)(1) requires a derating factor of 0.80 for 4-6 conductors. You apply this 0.80 multiplier to the 90°C column before checking against your breaker size.

Decision Tree: Pick Your Exact Aluminium Wire Size

Use this decision matrix to lock in the correct wire size for standard residential and light commercial installations. This path accounts for the NEC 110.14(C) termination rules and the NEC 310.12(A) dwelling service exception.

Installation Scenario NEC Rule Applied Required Column Final Wire Pick
100A Subpanel Feeder 110.14(C)(1)(a) - Default to 60°C for ≤100A unless lugs marked 75°C. 60°C 1/0 AWG AL (100A). Note: 1 AWG AL is acceptable if 75°C lugs are verified.
125A Subpanel Feeder 110.14(C)(1)(b) - Default to 75°C for >100A. 75°C 1/0 AWG AL (120A at 75°C).
150A Subpanel Feeder 110.14(C)(1)(b) - Default to 75°C for >100A. 75°C 2/0 AWG AL (135A) is too small. Use 3/0 AWG AL (155A) or 2/0 AWG Cu.
200A Residential Service 310.12(A) - Dwelling service exception allows 83% of rating (166A). 75°C 4/0 AWG AL (180A at 75°C, which is > 166A).
200A Commercial/Shop Service Standard sizing - No 83% dwelling exception. Must carry full 200A. 75°C 250 kcmil AL (205A at 75°C).
50A Hot Tub / RV Pedestal 110.14(C)(1)(a) - Default to 60°C for ≤100A. 60°C 4 AWG AL (55A) is too small. Use 3 AWG AL (65A) or 6 AWG Cu.
Sizing for Continuous Loads: If your load is continuous (operating for 3 hours or more, like a commercial heater or EV charger), the wire ampacity must be sized at 125% of the continuous load. A 40A continuous EV charger requires wire rated for 50A. At the 60°C column, that means you must step up to 4 AWG AL (55A), not 6 AWG AL.

What This Chart Cannot Tell You (Edge Cases & Limits)

An ampacity chart is only half the equation. Before you buy a 500-foot spool of aluminium feeder, you must account for three physical and electrical realities that NEC Table 310.16 ignores.

1. Voltage Drop Over Distance

Ampacity dictates whether the wire will melt; it does not dictate whether your equipment will actually run. NEC 310.15(B) includes an informational note recommending a maximum 3% voltage drop for branch circuits and 5% total for feeder and branch combined. If you are running a 100A subpanel 200 feet to a detached garage, 1/0 AWG AL will suffer roughly a 4.5% voltage drop at full load. You must upsize to 2/0 AWG AL to keep the drop under 3%, even though 1/0 is legally sufficient for heat dissipation. Use the Southwire Voltage Drop Calculator to verify your specific run length.

2. Physical Lug Fitment

Just because a wire has the correct ampacity doesn't mean it will physically fit into the breaker. A standard 100-amp main breaker lug is typically rated to accept a maximum of 1 AWG or 1/0 AWG. If you upsize to 2/0 AWG to mitigate voltage drop, the bare aluminium strands will not fit into the lug barrel. You will need to use a reducing pin connector or install a larger main breaker lug kit, which is often impossible on stock residential load centers. Always check the breaker datasheet for 'Wire Range' before upsizing.

3. Termination Prep and Oxidation

Aluminium oxidizes rapidly when exposed to air, creating a high-resistance layer that generates heat under load. The chart assumes perfect terminations. In practice, you must wire-brush the stripped aluminium conductor under a layer of anti-oxidant compound (like Noalox) immediately before inserting it into the lug. Furthermore, aluminium creeps under pressure; you must torque the lug to the manufacturer's exact inch-pound specification using a calibrated torque screwdriver, and re-torque it after the first thermal cycle if required by your local AHJ.