AWG Wire Gauge Chart

Solid-copper AWG sizes from 4/0 down to 20, with diameter in inches and millimeters, cross-section area, and ampacity at three insulation temperature ratings. Use this table to read a gauge stamp, compare sizes, or prepare a question for the ampacity tool — not to design or install wiring.

Find your size

Reference only — not a substitute for local electrical code. Ampacity values are from NEC 2023 Table 310.16 under specific conditions. Verify temperature rating, conduit fill, terminal limits, and the code adopted where the work is performed. Disclaimer

AWG Diameter (in) Diameter (mm) Area (mm²) 60 °C 75 °C 90 °C Note
4/0 AWG 0.4600 11.684 107.20 195 A 230 A 260 A Service entrance / large feeder conductor
3/0 AWG 0.4096 10.404 85.00 165 A 200 A 225 A Service entrance / large feeder
2/0 AWG 0.3648 9.266 67.40 145 A 175 A 195 A Service entrance / large feeder
1/0 AWG 0.3249 8.252 53.50 125 A 150 A 170 A Sub-panel feeder / large load
1 AWG 0.2893 7.348 42.40 110 A 130 A 145 A Sub-panel feeder / large load (conditions apply)
2 AWG 0.2576 6.544 33.60 95 A 115 A 130 A Large feeder (conditions apply)
3 AWG 0.2294 5.827 26.70 85 A 100 A 110 A Large feeder (conditions apply)
4 AWG 0.2043 5.189 21.20 70 A 85 A 95 A Feeder / high-load circuit (conditions apply)
6 AWG 0.1620 4.115 13.30 55 A 65 A 75 A Higher capacity runs (conditions apply)
8 AWG 0.1285 3.264 8.37 40 A 50 A 55 A Larger feeders / higher load (conditions apply)
10 AWG 0.1019 2.588 5.26 30 A 35 A 40 A Often associated with 30A copper (conditions apply)
12 AWG 0.0808 2.053 3.31 20 A 25 A 30 A Often associated with 20A copper branch (conditions apply)
14 AWG 0.0641 1.628 2.08 15 A 20 A 25 A Often associated with 15A copper branch (conditions apply)
16 AWG 0.0508 1.291 1.31 — — — Light duty extension / low current — no NEC ampacity rating
18 AWG 0.0403 1.024 0.82 — — — Low-current / lamp cord class — no NEC ampacity rating
20 AWG 0.0320 0.812 0.52 — — — Signal / electronics wire — no NEC ampacity rating

Solid copper · ASTM B258-18 dimensions · NEC 2023 Table 310.16 ampacity (where rated). Ampacity assumes 30 °C ambient and no more than three current-carrying conductors.

12 AWG sample (50 ft stranded THHN)

One short-length 12 AWG option for bench verification or shop experiments — not whole-house cable. Confirm the AWG stamp and insulation rating on the listing. Permanent wiring needs code and a qualified electrician.

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Electrical safety notice: This product is a sample-length conductor for workshop use. It is not a recommendation to rewire a circuit or bypass local inspection. See our disclaimer for limits of use.

How to read this chart

Cross-section circles of AWG 4/0 through 20 drawn to scale, showing lower gauge numbers mean larger diameter wire.

AWG numbering runs backwards from what you might expect: a lower gauge number means a thicker wire. 4/0 AWG at the top of the table is 0.4600 inches across — nearly half an inch of solid copper. By the time you reach 20 AWG at the bottom, the diameter is only 0.0320 inches, thinner than a sewing pin. The area column shows the same trend in square millimeters, and because resistance depends on cross-section area, thicker gauges carry more current with less voltage drop.

The three ampacity columns — 60 °C, 75 °C, and 90 °C — refer to the maximum operating temperature rating of the wire's insulation, not three flavors of "how much is safe." A conductor listed at 30 A in the 90 °C column still passes through terminals, breakers, and conduit fittings rated for lower temperatures. NEC rules cap the usable ampacity at the lowest rating in the thermal chain, which is often the 75 °C or 60 °C column. Never pick the highest number and call it done.

Three ampacity columns for 12 AWG showing 60C, 75C, 90C insulation ratings with 20A, 25A, 30A values respectively.

This table lists solid-copper dimensions. Stranded wire of the same AWG has the same total copper area but a slightly larger overall diameter because of gaps between strands. The ampacity values apply equally to solid and stranded copper under the stated conditions. For a focused current question — such as "what gauge for a 20 amp branch?" — open the ampacity lookup tool or the 20 amp guide.

Sizes without NEC ampacity

AWG 16, 18, and 20 appear with diameter and area but show "—" in all three ampacity columns. These are signal, lamp-cord, and electronics classes — NEC Table 310.16 does not list a current rating for them in residential power contexts. The aught sizes (4/0, 3/0, 2/0, 1/0) are pronounced "four-aught," "three-aught," and so on; they are service-entrance and large feeder conductors, not branch-circuit wire.

This chart covers copper only. Aluminum and copper-clad aluminum conductors have different ampacity values and termination rules — they are out of scope here. For a broader comparison across insulation types and installation methods, see the ampacity chart.

FAQ

What does AWG stand for in wire sizes?

AWG stands for American Wire Gauge, a standard sizing system for round solid electrical conductors dating to 1857. Lower AWG numbers mean thicker wire; higher numbers mean thinner wire. The system is defined by ASTM B258-18, which fixes the diameter for every size from 4/0 (0.4600 in) down to 20 AWG (0.0320 in).

Is this chart a substitute for local electrical code?

No. This chart is a workshop size reference built from ASTM B258-18 dimensions and NEC 2023 Table 310.16 ampacity values for copper conductors under specific conditions (30 °C ambient, no more than three current-carrying conductors). Local jurisdictions adopt different NEC editions, add amendments, and derate for temperature, conduit fill, and continuous loads. For any installed circuit, follow the code enforced where the work is performed and have the work inspected.

Does a lower AWG number mean thicker or thinner wire?

Lower AWG means thicker wire. 4/0 AWG has a diameter of 0.4600 inches (11.684 mm); 20 AWG has a diameter of 0.0320 inches (0.812 mm). The numbering comes from the number of drawing passes used in the original 19th-century wire mill — more passes produced thinner wire, so higher gauge numbers correspond to smaller cross-sections.

Why does the same AWG have three ampacity columns — 60 °C, 75 °C, and 90 °C?

The three columns reflect the temperature rating of the wire insulation, not three choices of "how much current is safe." A 12 AWG copper conductor rated 60 °C (TW, UF) is listed at 20 A; the same conductor with 75 °C insulation (THWN, XHHW) is listed at 25 A; with 90 °C insulation (THHN, XHHW-2) at 30 A. You may not use the 90 °C column by itself — terminal ratings, equipment listing, and conduit fill often cap the usable ampacity at the 75 °C or 60 °C column. Conditions apply per NEC 310.16. See the ampacity chart for a deeper comparison.

What AWG do I need for a 20-amp circuit?

For a 20-amp copper branch circuit, 12 AWG is the common residential size — this chart lists 12 AWG at 20 A in the 60 °C column. That association assumes copper conductors, the listed insulation rating, and standard installation conditions; it is not universal. For the full decision (including when 10 AWG is required for voltage drop or continuous loads), see the dedicated page on gauge selection for 20-amp circuits.

Sources

Diameters and cross-section areas follow ASTM B258-18. Ampacity values are from NFPA 70 National Electrical Code 2023, Table 310.16, for copper conductors at 30 °C ambient with no more than three current-carrying conductors. Both standards are referenced for accuracy; this page does not reproduce their full text or substitute for the adopted code.

  • ASTM B258-18 — Standard Nominal Diameters and Cross-Sectional Areas of AWG Sizes
  • NFPA 70 NEC 2023, Table 310.16 — Allowable Ampacities of Insulated Conductors (Copper)

See the site disclaimer for limits of use.

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