AWG wire size chart

Physical dimensions computed exactly from the gauge definition, copper resistance from the international annealed-copper standard, and code ampacities where the NEC defines them.

AWG	Diameter (in)	Diameter (mm)	Area (kcmil)	Area (mm²)	Ω per km (Cu)
4/0	0.4600	11.684	211,600	107	0.161
3/0	0.4096	10.405	167,806	85	0.203
2/0	0.3648	9.266	133,077	67.4	0.256
1	0.2893	7.348	83,693	42.4	0.407
2	0.2576	6.544	66,371	33.6	0.513
3	0.2294	5.827	52,635	26.7	0.646
4	0.2043	5.189	41,741	21.2	0.815
5	0.1819	4.621	33,102	16.8	1.03
6	0.1620	4.115	26,251	13.3	1.3
7	0.1443	3.665	20,818	10.5	1.63
8	0.1285	3.264	16,510	8.37	2.06
9	0.1144	2.906	13,093	6.63	2.6
10	0.1019	2.588	10,383	5.26	3.28
11	0.0907	2.305	8,234	4.17	4.13
12	0.0808	2.053	6,530	3.31	5.21
13	0.0720	1.828	5,178	2.62	6.57
14	0.0641	1.628	4,107	2.08	8.29
15	0.0571	1.450	3,257	1.65	10.4
16	0.0508	1.291	2,583	1.31	13.2
17	0.0453	1.150	2,048	1.04	16.6
18	0.0403	1.024	1,624	0.823	20.9
19	0.0359	0.912	1,288	0.653	26.4
20	0.0320	0.812	1,022	0.518	33.3
21	0.0285	0.723	810	0.41	42
22	0.0254	0.644	642	0.326	53
23	0.0226	0.573	509	0.258	66.8
24	0.0201	0.511	404	0.205	84.2
25	0.0179	0.455	320	0.162	106
26	0.0159	0.405	254	0.129	134
27	0.0142	0.361	202	0.102	169
28	0.0126	0.321	160	0.081	213
29	0.0113	0.286	127	0.0642	268
30	0.0100	0.255	101	0.0509	339
31	0.0089	0.227	80	0.0404	427
32	0.0080	0.202	63	0.032	538
33	0.0071	0.180	50	0.0254	679
34	0.0063	0.160	40	0.0201	856
35	0.0056	0.143	32	0.016	1080
36	0.0050	0.127	25	0.0127	1360
37	0.0045	0.113	20	0.01	1720
38	0.0040	0.101	16	0.00797	2160
39	0.0035	0.090	12	0.00632	2730
40	0.0031	0.080	10	0.00501	3440

NEC allowable ampacity, copper conductors

AWG	60 °C (TW, UF)	75 °C (THW, THWN)	90 °C (THHN, XHHW)
14	15 A	20 A	25 A
12	20 A	25 A	30 A
10	30 A	35 A	40 A
8	40 A	50 A	55 A
6	55 A	65 A	75 A
4	70 A	85 A	95 A
3	85 A	100 A	115 A
2	95 A	115 A	130 A
1	110 A	130 A	145 A
1/0	125 A	150 A	170 A
2/0	145 A	175 A	195 A
3/0	165 A	200 A	225 A
4/0	195 A	230 A	260 A

Using these numbers together

Pick the conductor size from the ampacity table first, then check voltage drop against the resistance column: drop = current × resistance-per-km × length. If a run fails the drop budget, go up a size even though ampacity allowed the smaller wire. Conductor resistance assumes solid annealed copper at 20 °C; stranded building wire measures within about 1% of these figures because ASTM compacts the stranding to the same overall area.

Frequently asked questions

What does the AWG number actually mean?

It counts draw passes. Every step of 6 gauges halves the diameter, and every step of 3 doubles or halves the cross-sectional area, which is why the series is geometric rather than linear. 36 AWG is defined as exactly 0.005 inch and 4/0 as exactly 0.46 inch, and everything between follows from those two anchors.

Why do ampacity rules ignore the smaller sizes?

NEC Table 310.16 starts at 14 AWG because building wiring rarely uses anything thinner; below that, current limits come from the equipment standard or connector rating instead. The 90 °C column exists mainly as a derating starting point, since terminations are usually rated 60 or 75 °C.

Does resistance depend on temperature?

The chart's resistance is at 20 °C. Copper's resistivity rises about 0.39% per °C, so a conductor at 75 °C carries roughly 20% more resistance than the tabulated value. Voltage-drop checks on long runs should use the operating temperature.

Dimensions per ASTM B258 (d = 0.005″ × 92^((36−n)/39); 4/0 = 0.4600″). Resistance from IACS annealed-copper resistivity, 0.017241 Ω·mm²/m at 20 °C. Ampacities per NEC Table 310.16, three conductors, 30 °C ambient; derating and termination rules apply.