Wire Gauge Chart

American Wire Gauge is a standardized scale for the size of round electrical conductors. The counter-intuitive part: a smaller AWG number means a thicker wire. The scale is geometric — every 6 gauge steps roughly halves the diameter, and every 3 steps roughly halves the cross-sectional area.

No. AWG follows a logarithmic scale defined by ASTM B258, while metric mm² conductors (IEC 60228) come in a separate set of standard linear sizes, so the two rarely line up exactly. The right way to convert is to compute a gauge's true cross-sectional area and then compare it to the nearest standard mm² size — never treat them as a fixed one-to-one table.

Ampacity is the maximum current, in amperes, that a conductor can carry continuously without exceeding its temperature rating. It is not a single fixed number for a given gauge: it depends on the conductor material (copper carries more than aluminum at the same size), the temperature rating of the insulation (the 60/75/90 °C columns), the ambient temperature, and how many current-carrying conductors are bundled together. The ampacity figures on this chart come from NEC Table 310.16 and are the starting point, before those derating and terminal-rating adjustments.

A solid 12 AWG conductor measures 0.0808 inches (2.05 mm) in diameter, with a cross-sectional area of about 3.31 mm² (6.53 kcmil). Because the AWG scale is geometric you can estimate from there: a wire six gauges thinner (18 AWG) is roughly half that diameter, and three gauges thinner (15 AWG) is roughly half the area. The reference table above gives the exact diameter and area for every gauge.

It depends on the conductor material (copper vs aluminum), the insulation's temperature rating (the 60/75/90 °C columns), the ambient temperature, how many conductors are bundled together, and the overcurrent device protecting the circuit. The ampacity column on this chart is the NEC Table 310.16 starting point, before those real-world adjustments — always size to your specific installation and code.

Not directly. Wire gauge is chosen from the current the circuit carries (amps) and the length of the run — to keep voltage drop in check — not from the nominal system voltage. A 20-amp circuit uses 12 AWG copper whether it runs at 120 V or 240 V. Voltage matters only indirectly: at a higher voltage the same wattage draws fewer amps, and a long run can need a thicker wire than the ampacity table alone suggests in order to limit voltage drop.

For copper, a 20-amp circuit uses 12 AWG and a 30-amp circuit uses 10 AWG — those small-conductor sizes are fixed by the NEC 240.4(D) breaker caps rather than raw ampacity. At 50 amps that cap no longer applies: 8 AWG copper is rated 50 A in the 75 °C column, though many installations step up to 6 AWG for derating or voltage-drop headroom. Enter any current in the gauge-by-amperage selector above, then confirm against your load calculation and local code.

Service-entrance and dwelling feeder conductors are a special case. NEC 310.12 lets them be sized smaller than the branch-circuit ampacity table would imply, so a 100-amp dwelling service is commonly 4 AWG copper (2 AWG aluminum) and a 200-amp service 2/0 copper (4/0 aluminum). Those differ from the Table 310.16 figures used elsewhere on this chart, which apply to ordinary branch circuits and feeders. Service sizing also depends on the load calculation and local amendments, so confirm the final size with your inspector or a licensed electrician.

Size the wire to the circuit's amperage and its breaker. A 30-amp electric dryer uses 10 AWG copper — the NEC 240.4(D) cap for 10 AWG. A 40-amp range or oven uses 8 AWG copper, and a 50-amp range or EV-charger circuit also lands on 8 AWG (rated 50 A in the 75 °C column), though 6 AWG is common for derating or voltage-drop headroom on long runs. Enter the appliance's circuit rating in the gauge-by-amperage selector above, then confirm against the appliance nameplate and your local code.

On a branch circuit, copper 12-gauge is protected at 20 amps and 10-gauge at 30 amps under the NEC 240.4(D) small-conductor rule (14-gauge is 15 amps). The raw ampacity in Table 310.16 is higher — 12 AWG copper reaches 25 A in the 75 °C column and 30 A at 90 °C before derating — but the breaker cap is what governs the circuit. Conductors larger than 10 AWG are sized straight from the ampacity columns instead of a fixed cap.

Because NEC 240.4(D) caps the overcurrent protection for small conductors separately from raw ampacity. Regardless of the larger figures in the ampacity table, copper is limited to 15 A at 14 AWG, 20 A at 12 AWG, and 30 A at 10 AWG (aluminum: 15 A at 12 AWG, 25 A at 10 AWG). Confusing this breaker cap with raw ampacity is the single most common wiring mistake.

Those are the temperature rating of the conductor's insulation. You read ampacity from the column that matches your wire's insulation, but the usable value is also limited by the temperature rating of the terminals and lugs at each end of the run (NEC 110.14(C)) — for most everyday equipment that means the 75 °C column.

Yes. Aluminum carries less current than copper at the same gauge, so an aluminum conductor is typically one to two AWG sizes larger for the same load, and aluminum is not rated below 12 AWG. This chart lists copper and aluminum ampacities side by side so you can compare directly.

For most home speaker runs, 16 AWG is fine up to roughly 25 feet on an 8-ohm speaker; step up to 14 AWG for longer runs or 4-ohm loads, and 12 AWG for very long runs where you want minimal resistance. Speaker wire carries low-voltage audio rather than mains power, so it is not governed by the NEC ampacity rules used elsewhere on this chart — the goal is simply to keep the wire's resistance low relative to the speaker so you do not lose signal. When in doubt, thicker (lower-gauge) wire is the safe choice.

Measure the diameter of the bare metal conductor — not the insulation — with calipers or a dedicated wire-gauge tool, then match that diameter to the reference table. For stranded wire, the overall bundle reads larger than the equivalent solid gauge, so measure one strand and scale by the strand count. Quickest of all: many cables print the size right on the jacket, such as "12 AWG" or "2.5 mm²".