Guide Topics
AWG Wire Size Chart & Reference Guide
American Wire Gauge (AWG) reference table with diameters, resistance, ampacity and the nearest metric sizes, 18 AWG to 4/0.
Quick AWG Reference - Most Common Sizes
14 AWG
- • Diameter: 1.628 mm
- • 15 A circuits
12 AWG
- • Diameter: 2.052 mm
- • 20 A circuits
10 AWG
- • Diameter: 2.588 mm
- • 30 A circuits
6 AWG
- • Diameter: 4.115 mm
AWG Wire Size Table
| AWG | Diameter (mm) | Diameter (inch) | Area (mm²) | Ω/1000 ft, solid annealed copper, 20 °C (NIST Handbook 100) | Cu Ampacity 75 °C | Al Ampacity 75 °C |
|---|---|---|---|---|---|---|
| 18 | 1.024 | 0.0403 | 0.8209 | 6.39 | — | — |
| 16 | 1.290 | 0.0508 | 1.307 | 4.02 | — | — |
| 14 | 1.628 | 0.0641 | 2.083 | 2.52 | 20* | — |
| 12 | 2.052 | 0.0808 | 3.309 | 1.59 | 25* | 20* |
| 10 | 2.588 | 0.1019 | 5.26 | 0.9988 | 35* | 30* |
| 8 | 3.264 | 0.1285 | 8.366 | 0.6281 | 50 | 40 |
| 6 | 4.115 | 0.1620 | 13.3 | 0.3952 | 65 | 50 |
| 4 | 5.189 | 0.2043 | 21.15 | 0.2485 | 85 | 65 |
| 3 | 5.827 | 0.2294 | 26.66 | 0.1971 | 100 | 75 |
| 2 | 6.543 | 0.2576 | 33.63 | 0.1563 | 115 | 90 |
| 1 | 7.348 | 0.2893 | 42.41 | 0.1239 | 130 | 100 |
| 1/0 | 8.252 | 0.3249 | 53.51 | 0.09825 | 150 | 120 |
| 2/0 | 9.266 | 0.3648 | 67.44 | 0.07793 | 175 | 135 |
| 3/0 | 10.404 | 0.4096 | 85.03 | 0.06182 | 200 | 155 |
| 4/0 | 11.684 | 0.4600 | 107.2 | 0.04901 | 230 | 180 |
* Limited by NEC 240.4(D) small conductor rule. Copper: 14 AWG max 15 A, 12 AWG max 20 A, 10 AWG max 30 A protection. Aluminum: 12 AWG max 15 A, 10 AWG max 25 A protection.
AWG to Metric Wire Size Conversion
Common AWG to mm² Conversions
| AWG | mm² | Nearest Metric |
|---|---|---|
| 14 AWG | 2.083 | 2.5 mm² |
| 12 AWG | 3.309 | 4 mm² |
| 10 AWG | 5.26 | 6 mm² |
| 8 AWG | 8.366 | 10 mm² |
| 6 AWG | 13.3 | 16 mm² |
| 4 AWG | 21.15 | 25 mm² |
| 2 AWG | 33.63 | 35 mm² |
| 1/0 AWG | 53.51 | 50 mm² |
AWG System Explained
The AWG system is logarithmic - each 3-gauge decrease doubles the cross-sectional area.
Smaller AWG numbers = larger wire diameters. AWG 0000 (4/0) is the largest standard size.
For sizes larger than 4/0, kcmil (MCM) is used, representing thousands of circular mils.
Formula: Diameter(n) = 0.005 × 92^((36-n)/39) inches
The Math Behind AWG — ASTM B258 and the Geometric Progression
AWG is not arbitrary. The numbers in the table above derive from a specific geometric progression defined by ASTM B258 (the Standard Specification for Standard Nominal Diameters and Cross-Sectional Areas of AWG Sizes of Solid Round Wires Used as Electrical Conductors). Understanding the math lets you derive any AWG specification from first principles.
The geometric definition
AWG is anchored at two endpoints: 0000 (4/0) AWG = 0.4600″ diameter, and 36 AWG = 0.0050″ diameter. The 38 sizes between 4/0 and 36 are spaced in a geometric progression.
Above 4/0 — kcmil takes over
AWG runs out at 4/0 (0.4600″). Larger conductors are specified by cross-sectional area in kcmil (thousands of circular mils). 1 circular mil = the area of a circle with diameter 0.001 inch (1 mil).
Stranded vs solid
All AWG diameters in the table above are for SOLID conductor.
- Stranded: in raceways, 8 AWG and larger shall be stranded unless permitted or required elsewhere to be solid (2023 NEC 310.3(C)).
Insulation type
Two conductors of identical AWG can have very different ampacities depending on insulation rating. NEC 310.16 organizes by insulation temperature class:
- 60 °C: TW, UF
- 75 °C: RHW, THHW, THW, THWN, XHHW, XHWN, USE, ZW
- 90 °C: THHN, THWN-2, XHHW-2, USE-2, RHW-2, and others
Why 12 AWG ampacity is 25 A (75 °C column) but the breaker can’t exceed 20 A
NEC 240.4(D) is the “small-conductor rule”: regardless of higher 310.16 ampacity, the OCPD on 14, 12, 10 AWG copper is capped:
- 14 AWG: ampacity 20 A (75 °C), OCPD max 15 A
- 12 AWG: ampacity 25 A (75 °C), OCPD max 20 A
- 10 AWG: ampacity 35 A (75 °C), OCPD max 30 A