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AWG Wire Gauge Diameter Chart

Guide · Updated October 28, 2026

American Wire Gauge (AWG, also Brown & Sharpe gauge) sizes solid round nonferrous wire such as copper and aluminum. Unlike sheet gauges, AWG is defined by a formula in ASTM B258: 36 AWG is 0.0050 in, 0000 AWG is 0.4600 in, and there are 39 equal geometric steps between them. So d = 0.005 × 92^((36 − n) ÷ 39) inches, with 0 = 0, 00 = −1, 000 = −2 and 0000 = −3. Every 6 gauges halves the diameter, and every 3 gauges halves the area. AWG is not used for steel wire, music wire or sheet steel, which have their own gauges.

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Step by step

  1. Mic the bare wire: Strip insulation and measure the conductor, not the jacket.
  2. Look up the gauge: Match the diameter to the chart.
  3. Handle stranded wire: Stranded conductors are larger than the solid diameter; count strands and mic one.
  4. Use the formula: For gauges not listed, calculate d = 0.005 × 92^((36 − n) ÷ 39).
  5. Size holes: Drill or bore with clearance over the insulated OD for grommets and pass-throughs.
  6. Check the mic: Verify zero and a gage block before measuring small wire.

AWG diameter chart (ASTM B258 formula)

Circular mils equal the diameter in thousandths of an inch squared. Real wire is made to a tolerance around these nominal values, typically about 1% of diameter for copper magnet wire, so expect small differences on the mic.

Rules of thumb

Three gauges apart doubles or halves the cross-section; ten gauges apart changes area by about 10 times. 10 AWG is about 0.10 in, 1 mm is close to 18 AWG (1.024 mm), and 0.5 mm is close to 24 AWG (0.511 mm). These help you identify wire quickly without a chart.

Shop uses

Machinists meet AWG when wiring machines and fixtures, drilling for wire pass-throughs, sizing EDM wire (usually given in inches or mm, such as 0.010 in, which is close to 30 AWG), using wire as shim, and making three-wire substitutes or locating pins from known copper wire in an emergency. For anything precise, use certified pin gages instead of wire.

Worked example: identify a wire

You mic a bare solid conductor at 0.064 in. 14 AWG is 0.0641 in, so it is 14 AWG. A conductor at 0.081 in is 12 AWG (0.0808 in).

Worked example: calculate 22 AWG

d = 0.005 × 92^((36 − 22) ÷ 39) = 0.005 × 92^0.35897. ln 92 = 4.5218, × 0.35897 = 1.6232, e^1.6232 = 5.0697, so d = 0.0253 in, or 0.644 mm. Area = 25.3² = 642 circular mils.

Common problems

Measuring over insulation, treating stranded wire as solid, and confusing AWG with SWG (British Standard Wire Gauge) or steel wire gauge, which give different diameters for the same number. Electrical current ratings depend on insulation, temperature and code, so take ampacity from the NEC or your electrician, not from diameter alone.

FAQ

What is the diameter of 12 AWG wire?

0.0808 in (2.053 mm) solid.

What is the diameter of 14 AWG?

0.0641 in (1.628 mm).

What is the AWG formula?

d = 0.005 × 92^((36 − n) ÷ 39) inches.

Does a smaller gauge number mean bigger wire?

Yes, AWG numbers go up as the wire gets thinner.

Is AWG the same as sheet metal gauge?

No, they are different systems with different sizes.

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General shop information only — follow your drawing, tool maker's data and your quality system.