NEC Wire Size Ampacity Chart: Copper & Aluminum Amp Ratings

Wire Size Ampacity Chart (NEC)

Ampacity is the maximum current a wire can carry continuously without exceeding its insulation's temperature rating, and in the United States it's set by NEC Table 310.16 based on wire gauge, conductor material (copper or aluminum), and insulation temperature rating (60°C, 75°C, or 90°C). The amperage rating for a wire always drops as gauge number increases — a lower AWG number means a physically larger conductor with less resistance, which is why 10 AWG carries more current than 14 AWG, and why 4 AWG carries more than 10 AWG.

The chart below covers the copper wire sizes used in the large majority of residential, commercial, and light industrial circuits, from small lighting branch circuits up to sub-panel feeders.

Understanding National Electrical Code Wire Size Requirements

The National Electrical Code doesn't just publish a single ampacity number per gauge — the rating depends on which insulation temperature column applies, since 60°C, 75°C, and 90°C insulation types handle heat differently before conductor or insulation damage occurs. In practice, the equipment terminal rating (breakers, outlets, disconnects) usually governs which column applies rather than the wire's own insulation rating. Under NEC 110.14(C), circuits rated 100A or less generally use the 60°C column unless all connected equipment is listed for 75°C, and most modern breakers and devices are dual-rated for 60/75°C — which is why the 75°C column is the practical reference point for most residential and light commercial work, even when 90°C-rated wire like THHN is installed.

Table 310.16 itself only reflects a baseline installation condition — three or fewer current-carrying conductors in a raceway, cable, or earth, at a 30°C (86°F) ambient temperature. Any installation that deviates from that baseline needs correction or adjustment factors applied before the table value can be treated as the wire's actual usable ampacity.

Factors That Reduce Wire Ampacity Below the Chart Value

Chart values represent a best-case scenario, and several common installation conditions require derating the wire below its listed ampacity:

• Ambient temperature above 30°C — NEC 310.15 correction factors reduce ampacity further as ambient temperature rises, which matters for wiring run through hot attics, near furnaces, or in outdoor conduit exposed to direct sun
• Conductor bundling — when more than three current-carrying conductors share a raceway, cable, or conduit, adjustment factors reduce ampacity because the conductors can't dissipate heat as effectively as an isolated wire; four to six conductors typically drop ampacity to 80% of the table value, and the percentage decreases further as conductor count rises
• Long conductor runs — while not a code-mandated ampacity reduction, voltage drop across long circuit runs can make a wire that meets ampacity requirements still perform poorly; NEC recommends keeping voltage drop under 3% for branch circuits and 5% for the combined feeder and branch circuit, which sometimes means upsizing wire beyond the ampacity minimum
• Continuous loads — circuits that carry their maximum current for three hours or more must be sized using the 125% rule, covered in more detail below

Continuous Loads and the 125% Rule

Under NEC 210.19 and 210.20, a continuous load — one expected to run at maximum current for three hours or more, such as lighting, EV charging, or HVAC equipment — requires both the wire and the breaker to be sized at 125% of the continuous load current, unless the equipment is specifically listed for 100% continuous duty. In practice, this means a 40A continuous load needs a circuit sized for 50A (40 × 1.25), which typically pushes the wire gauge up one step from what a simple non-continuous ampacity lookup would suggest. This is one of the most common reasons a wire size calculated from a raw amperage chart ends up undersized once the actual load profile of the circuit is factored in.

Copper vs Aluminum Wire Ampacity

Copper has lower electrical resistance than aluminum, so at any given gauge, copper wire carries more current before reaching the same operating temperature — which is why aluminum feeders and service entrance cables are typically sized one to two gauges larger than an equivalent copper installation. Aluminum's cost advantage per pound of conductor material is what keeps it in wide use for larger feeders and utility service entrance conductors despite the lower ampacity per gauge, since the larger aluminum conductor needed to match a copper circuit's ampacity is often still cheaper than the copper equivalent at larger wire sizes. Aluminum conductors also require anti-oxidant compound at connections and periodic torque checks, since aluminum is more prone to connection loosening from thermal expansion and contraction than copper.

10 AWG Wire Amp Rating

10 AWG copper wire is rated for 30A at 60°C, 35A at 75°C, and 40A at 90°C under NEC Table 310.16. In residential wiring, 10 AWG is the standard size for 30-amp circuits — common for window air conditioners, electric water heaters, and some dryer circuits — since most residential breakers and terminals are rated at the 60°C or 75°C column rather than the full 90°C figure. 10 AWG aluminum, by comparison, is rated lower at 25A/30A/35A across the same three columns, which is why aluminum branch circuits at this gauge are far less common in residential applications.

8 Gauge Wire Amp Rating

8 gauge copper wire carries 40A at 60°C, 50A at 75°C, and 55A at 90°C. The maximum amperage for 8 gauge wire in a real installation is generally taken as the 75°C column figure of 50A, since most modern breakers and equipment terminals are rated for 75°C — the 90°C figure of 55A can only be used if every component in the circuit, including the breaker and terminals, is also rated for 90°C, which is uncommon in standard residential and commercial equipment. 8 AWG is a common choice for 40-amp circuits such as electric cooktops, some subpanel feeds, and larger window units.

6 AWG Wire Amp Rating

6 AWG copper wire is rated for 55A at 60°C, 65A at 75°C, and 75A at 90°C, making it the standard size for 50A and 60A circuits, including many electric ranges, dryers on a 50A circuit, and sub-panel feeders serving detached garages or workshops. Its widespread use in these mid-size circuits makes it one of the most commonly stocked gauges in electrical supply houses.

Ampacity of 4 AWG Copper Wire

4 AWG copper wire is rated for 70A at 60°C, 85A at 75°C, and 95A at 90°C. This gauge is common for sub-panel feeders, larger electric ranges, and EV charging circuits, where the higher continuous current draw of the load requires stepping up from the smaller gauges used in standard branch circuits. Because EV charging is a continuous load under the 125% rule, a 4 AWG copper feeder is frequently paired with a 60A breaker for a 48A-rated Level 2 charger, rather than being pushed to its full 70A/85A rating.

2 AWG and 1/0 AWG Wire Amp Ratings

Moving up to larger feeder and service-entrance sizes, 2 AWG copper is rated for 95A/115A/130A across the 60/75/90°C columns, commonly used for 90A–100A subpanel feeders. 1/0 AWG copper steps up to 125A/150A/170A, a size frequently specified for 100A to 125A residential service feeders and larger detached-structure subpanels. At these larger gauges, conduit fill and conductor bending radius become practical installation constraints in addition to the ampacity requirement, so larger feeder sizing typically involves both an ampacity check and a conduit fill calculation.

Ampacity Chart for Aluminum Wire

Aluminum wire carries less current than copper at the same gauge because of its higher electrical resistance, which is why aluminum installations typically need to go one or two gauge sizes larger than copper to carry an equivalent load safely. Aluminum conductors intended for direct branch-circuit wiring are also generally listed starting at 12 AWG rather than the smaller gauges used in copper residential wiring.

What Wire Size Do You Need for 60 Amp or 65 Amp Circuits

For a 60-amp circuit, 6 AWG copper wire is the standard choice, since it's rated for 65A at the 75°C column — comfortably covering a 60-amp breaker with margin to spare, which is also why 6 AWG is the answer when the question is framed the other way around as "what size wire is rated for 65 amps." Aluminum installations of the same circuit typically need to step up to 4 AWG aluminum to reach the equivalent 65A rating at 75°C, reflecting aluminum's lower ampacity at any given gauge compared to copper. As with any circuit near the top of a wire's rated capacity, it's worth double-checking whether the load is continuous — if so, the 125% rule may call for stepping up to 4 AWG copper even on a 60A breaker to keep the conductor comfortably below its maximum rating during sustained full-load operation.

Quick Reference: Common Circuit Amperage to Wire Size