Wire Gauges

AWG wire gauge numbers seem to be a mixed bag of disconnected values upon first glance. However, there is a pattern to them. They are set up based upon a logarithmic scale. This is the same way decibels are related in sound energy measurement.

What does this mean? If you look at the diameter of a particular wire gauge, say AWG 14 you can see it has a diameter of 64.08 mils. Move up the table six positions to AWG 8 wire. You can see it has a diameter of 128.5 mils. This is a doubling of the diameter. Go up six more positions to AWG 2 size. You'll see it is 257.6 mils, a doubling of the AWG 8 size. The rule is that for every move of six positions in the table, the wire at the new level is one half the diameter, if you are finding the larger AWG number size, and double the diameter if you are finding the smaller AWG number size. Also, when the diameter of the wire is halved, the number of turns per inch doubles. This too is useful to remember.

Interestingly, if you compare the cross-sectional area of wire five AWG sizes apart, you can relate the two areas (approximately) through the number . For example, see that AWG 9 wire has an area of 0.01028 in². When we compare that to AWG 4 wire we see an area of 0.03278 in². These differ by a factor of 3.189, close to , and close enough to it to be useful as a rule of thumb. (Actually I think the factor they really do vary by is the square root of 10. If you would prefer to remember it that way, please feel free to do so!)

Related to the last one, if you move through ten positions, the area of a cross-section of the wire goes up by approximately the factor 10. Example: Look at AWG 10 wire. It has a diameter of 0.008155 in². Go down to AWG 20. It has an area of 0.0008023 in². Try one more, go to AWG 30. It has an area of 0.00007894 in². (OK, this isn't perfect, but it IS a good rule of thumb!)

Is that all? No, based on the same logarithmic principle, if you move twenty positions through the table, the diameter of the wire will vary by a factor of 10. For example look at the diameter of 30 AWG wire. It is 10.03 mils. If we move up the table to 10 AWG wire we see wire with a diameter of 101.9 mils.

And let's do one more, just because it is also kind of useful. Look at the resistance of AWG 6 wire. It is 4.016 per 1000 ft. at 20°C. Then look at AWG 16. It is 40.81 per 1000 ft. at 20°C. This too is a 10-fold increase in the resistance for a ten position move to a larger AWG number in the table. Indeed, a useful tidbit to recognize.

These handy rules of thumb make it easier to use this already useful table.

Wire Gauge Table - Standard Annealed Copper

			Cross Section @ 20°C		Ohms per 1000 ft
Wire Gauge	Diameter (Mils)	Turns per inch	Circular Mils	in2	0°C	20°C	50°C	75°C
0000	460.0	2.17	211600	0.1662	0.04516	0.04901	0.05479	0.05961
000	409.6	2.44	167800	0.1318	0.05695	0.0618	0.06909	0.07516
00	364.8	2.74	133100	0.1045	0.07181	0.07793	0.08712	0.09178
0	324.9	3.078	105500	0.08289	0.09055	0.09827	0.1099	0.1195
1	289.3	3.457	83690	0.06573	0.1142	0.1239	0.1385	0.1507
2	257.6	3.734	66370	0.05213	0.1440	0.1563	0.1747	0.1900
3	229.4	4.359	52640	0.04134	0.1816	0.1970	0.2203	0.2396
4	204.3	4.895	41740	0.03278	0.2289	0.2485	0.2778	0.3022
5	181.9	5.498	33100	0.02600	0.2887	0.3133	0.3502	0.3810
6	162.0	6.173	26250	0.02062	0.3640	0.3951	0.4416	0.4805
7	144.3	6.930	20820	0.01635	0.4590	0.4982	0.5569	0.6059
8	128.5	7.782	16510	0.01297	0.5788	0.6282	0.7023	0.7640
9	114.4	8.741	13090	0.01028	0.7299	0.7921	0.8855	0.9633
10	101.9	9.814	10380	0.008155	0.9203	0.9989	1.117	1.215
11	90.74	11.02	8234	0.006467	1.161	1.260	1.408	1.532
12	80.81	12.37	6530	0.005129	1.463	1.588	1.775	1.931
13	71.96	13.90	5178	0.004067	1.845	2.003	2.239	2.436
14	64.08	15.61	4107	0.003225	2.327	2.525	2.823	3.071
15	57.07	17.52	3257	0.002558	2.934	3.184	3.560	3.873
16	50.82	19.68	2583	0.002028	3.700	4.016	4.489	4.884
17	45.26	22.09	2048	0.001609	4.666	5.064	5.660	8.158
18	40.30	24.81	1624	0.001276	5.883	6.385	7.138	7.765
19	35.89	27.86	1288	0.001012	7.418	8.051	9.001	9.792
20	31.96	31.29	1022	0.0008023	9.355	10.15	11.35	12.35
21	28.45	35.15	810.1	0.0006363	11.80	12.80	14.31	15.57
22	25.35	39.45	642.4	0.0005046	14.87	16.14	18.05	19.63
23	22.57	44.31	509.5	0.0004002	18.76	20.36	22.76	24.76
24	20.10	49.75	404.0	0.0003173	23.65	25.67	28.70	31.22
25	17.90	55.87	320.4	0.0002517	29.82	32.37	36.18	39.36
26	15.94	62.74	254.1	0.0001996	37.61	40.81	45.63	49.64
27	14.20	70.42	201.5	0.0001583	47.42	51.47	57.53	62.59
28	12.64	79.11	159.8	0.0001255	59.80	64.90	72.55	78.93
29	11.26	88.81	126.7	0.00009953	75.40	81.83	91.48	99.52
30	10.03	99.70	100.5	0.00007894	95.08	103.2	115.4	125.5
31	8.928	112.0	79.70	0.00006260	119.9	130.1	145.5	158.2
32	7.950	125.8	63.21	0.00004964	151.2	164.1	183.4	199.5
33	7.080	141.2	50.13	0.00003937	190.6	206.9	231.3	251.6
34	6.305	158.6	39.75	0.00003122	240.4	260.9	291.7	317.3
35	5.015	199.4	31.52	0.00002476	303.1	329.0	367.8	400.1
36	5.000	200.0	25.00	0.00001964	382.2	414.8	463.7	504.5
37	4.453	224.6	19.83	0.00001557	482.0	523.1	584.8	636.2
38	3.965	252.2	15.72	0.00001235	607.8	659.6	737.4	802.2
39	3.531	283.2	12.47	0.000009793	766.4	831.8	929.8	1012
40	3.145	318.0	9.888	0.000007766	966.5	1049	1173	1276

Adapted from "Wire Table, Standard Annealed Copper - American Wire Gauge (B. & S.) English Units"

"Weast, Robert C., Ph.D. (1971-1972). CRC Handbook of Chemistry and Physics 52nd Edition. Cleveland, Ohio, The Chemical Rubber Co. "