Electrical Reference Library · Wall Charts

Wire Gauge (AWG) Size & Dimension Chart

AWG and kcmil sizes with the nominal bare solid-conductor diameter and cross-sectional area, for identifying and converting wire sizes. It is not an ampacity chart.

Ref EL-0048ASTM B258ASTM B3

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

American Wire Gauge (AWG) is a geometric numbering system for conductor size. ASTM B258 defines the nominal diameters. A smaller AWG number is a larger wire. Every 3 gauge steps roughly doubles the area, and every 6 steps roughly doubles the diameter. Sizes larger than 4/0 are given in kcmil (thousands of circular mils).

How to identify

Read the size on the insulation print line. This is the most reliable method.
On bare conductors, use a wire gauge plate on solid wire only. A stranded conductor has a larger OD than a solid wire of the same AWG and will read about one size too large.
After stripping, a caliper on a solid conductor can be compared to the diameter column below.

Dimension table (bare solid conductor, nominal)

AWG / kcmil	Diameter (in)	Diameter (mm)	Area (circular mils)	Area (mm²)
18	0.0403	1.02	1,620	0.823
16	0.0508	1.29	2,580	1.31
14	0.0641	1.63	4,110	2.08
12	0.0808	2.05	6,530	3.31
10	0.1019	2.59	10,380	5.26
8	0.1285	3.26	16,510	8.37
6	0.1620	4.11	26,240	13.3
4	0.2043	5.19	41,740	21.2
3	0.2294	5.83	52,620	26.7
2	0.2576	6.54	66,360	33.6
1	0.2893	7.35	83,690	42.4
1/0	0.3249	8.25	105,600	53.5
2/0	0.3648	9.27	133,100	67.4
3/0	0.4096	10.40	167,800	85.0
4/0	0.4600	11.68	211,600	107.2
250 kcmil	—	—	250,000	126.7
350 kcmil	—	—	350,000	177.3
500 kcmil	—	—	500,000	253.4

Diameters for kcmil sizes are left blank because these sizes are always stranded, and the OD depends on the stranding class and whether the conductor is compact.

Key points

1 circular mil is the area of a circle 0.001 in in diameter. 1 kcmil = 1,000 circular mils, which is about 0.5067 mm².
Metric (IEC 60228) sizes such as 2.5 mm² or 4 mm² do not exactly match any AWG size. Check the application before substituting one for the other.
Insulated OD depends on the insulation type and thickness. Get it from the manufacturer data when you size conduit fill or glands.

Common mistakes

Using this chart to pick a breaker or load. Ampacity comes from NEC 310.16 and related tables, not from wire diameter.
Gauging stranded wire with a solid-wire plate.
Confusing AWG with other gauge systems used for sheet metal or tubing.

Governing standards: ASTM B258 (nominal diameters and areas of AWG sizes); ASTM B3 (soft copper wire); ASTM B8 (stranded conductors); IEC 60228 (metric conductor sizes).

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

More in Wall Charts

← All Electrical sheets