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Wire Gauge Chart
AWG sizes with diameter, circular mils and mm².
| AWG | Diameter (in) | Diameter (mm) | Circular mils | Area (mm²) |
|---|---|---|---|---|
| 4/0 | 0.4600 | 11.684 | 211,600 | 107.22 |
| 3/0 | 0.4096 | 10.405 | 167,806 | 85.03 |
| 2/0 | 0.3648 | 9.266 | 133,077 | 67.43 |
| 1/0 | 0.3249 | 8.251 | 105,535 | 53.48 |
| 1 | 0.2893 | 7.348 | 83,693 | 42.41 |
| 2 | 0.2576 | 6.544 | 66,371 | 33.63 |
| 4 | 0.2043 | 5.189 | 41,741 | 21.15 |
| 6 | 0.1620 | 4.115 | 26,251 | 13.30 |
| 8 | 0.1285 | 3.264 | 16,510 | 8.37 |
| 10 | 0.1019 | 2.588 | 10,383 | 5.26 |
| 12 | 0.0808 | 2.053 | 6,530 | 3.31 |
| 14 | 0.0641 | 1.628 | 4,107 | 2.08 |
| 16 | 0.0508 | 1.291 | 2,583 | 1.31 |
| 18 | 0.0403 | 1.024 | 1,624 | 0.82 |
| 20 | 0.0320 | 0.812 | 1,022 | 0.52 |
| 22 | 0.0253 | 0.644 | 642 | 0.33 |
Diameters are bare conductor. Every third gauge roughly halves the area, and every six gauges roughly halves the diameter — both consequences of the geometric progression rather than coincidences. Ampacity is a separate question that depends on insulation, ambient temperature and how conductors are bundled.
AWG is a geometric progression, not an arbitrary list — each step changes diameter by a fixed factor. That means these figures are computed from the definition rather than copied, and they are exact for every size including the aught gauges.
Why use this tool?
Computed, not transcribed
Derived from the AWG geometric definition, so every row is exact and internally consistent.
Four units
Diameter in inches and millimetres, circular mils for voltage drop, mm² for metric specs.
The rules of thumb
Every three gauges roughly halves the area; every six roughly halves the diameter. Both fall out of the progression.
Not ampacity
This is geometry. What a conductor may safely carry depends on insulation, temperature and bundling.
How this wire gauge chart works
Diameter in mils is five times 92 raised to the power of (36 minus the gauge number) over 39. That single expression generates the entire system, including the aught sizes which take negative gauge numbers — 4/0 is n = −3.
Because it is geometric rather than arbitrary, the familiar shortcuts are exact consequences rather than approximations. Three gauge steps change area by almost exactly a factor of two; six steps change diameter by the same.
Circular mils is simply the diameter in mils squared — no π involved, which is the whole point of the unit. It makes the voltage-drop formula clean, which is why electricians still use it.
How to use it
Step 1: Find your gauge
Printed on the cable jacket, or measure the bare conductor.
Step 2: Read across
Diameter, circular mils and metric area.
Step 3: Use circular mils for drop
It is the figure the voltage drop formula wants.
Step 4: Check ampacity separately
That depends on insulation, ambient temperature and bundling, not on geometry.
Example usage
- Common branch circuit sizes
- 14 AWG is 0.0641 in — 4,107 circular mils. 12 AWG is 0.0808 in and 6,530 circular mils, about 59% more copper.
- The three-gauge rule
- 10 AWG is 10,384 circular mils against 13 AWG's 5,178 — almost exactly double, three steps apart.
- Service entrance sizes
- 4/0 is 0.46 in diameter and 211,600 circular mils, over fifty times the area of 14 AWG.
Frequently asked questions
What is the diameter of 12 AWG wire?
0.0808 inches, or 2.053 mm, giving 6,530 circular mils. That is the bare conductor, excluding insulation.
Why does a higher AWG number mean thinner wire?
The number originally counted the drawing operations needed to reach that size — more passes meant thinner wire. The scale runs backwards for that historical reason.
What is a circular mil?
The area of a circle one mil in diameter, which makes it simply the diameter in mils squared. Dropping π out of the arithmetic is exactly why the unit exists.
How much bigger is each gauge step?
Roughly 26% more area per step down. Three steps almost exactly doubles the area and six steps doubles the diameter — consequences of the geometric progression.
Does this tell me what current a wire can carry?
No. Ampacity depends on insulation rating, ambient temperature, how many conductors are bundled and the code in force locally. This is geometry only.
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