Bare Solid Copper Wire Properties & Gauge Conversions

Values presented here are standards available for many independent publications, but ultimately they all originate from the American Wire Gauge (AWG) system (also aka the Brown and Sharp - B&S - gauge). It has been in existence since the mid 1800s in the U.S. and Canada. Dimensions apply to most solid cylindrical rods regardless of material - copper, aluminum, plastic, carbon fiber, etc.

Note that as wire gauge number is increased the wire diameter decreases. Although it might seem somewhat backward, there is a good reason for it. Originally, it was related to the number of time a wire needed to be drawn through an extraction die in order to achieve the final wire size.

By definition, 36 AWG* is 0.0050 inches in diameter, and 0000 (four-ought)* is 0.4600 inches in diameter. The ratio of these diameters is 92, and there are 40 gauge sizes from #36 to #0000, or 39 steps. Using this ratio, wire gauge sizes vary geometrically according to the following formula: The diameter of a 36 AWG wire is:

AWG wire diameter equation for solid wire - RF Cafe

Those equations were used to calculate the values in the table below. Note that for one-ought cable you plug in n=0, for two-ought plug in n=-1, for three-ought plug in n=-2, and for four-ought plug in n=-3.

Accordingly, the ASTM B 258-02 standard defines the ratio between successive sizes to be the 39th root of 92, or approximately 1.1229322.

AWG wire gauge equation for solid wire - RF Cafe

Stranding designation of a/b means a number of b gauge wires. E.g., 7/44 means 7 strands of 44 AWG solid wire.

Note: Just a 3 dB change in power represents a doubling (or halving) of power, a change of 3 wire sizes represents approximately a doubling (or halving) of cross-sectional area.

See wire gauge conversion chart at bottom of page. Values given at 25 °C, and are based on ideal parameters of pure copper. Here is a table of fusing current of various wire sizes.

A circular mil is the cross-sectional area of a circle with a diameter of 1 mil (1/000th of an inch). NIST lists the density of pure copper as 8.92E+00 g/cm³, and is used here to calculate weight.

AWG (solid)	Approx. O.D.		Circular Mil Area	Weight (lbs/1000 ft)	Weight (kg/km)	Resistance (Ω/1000 ft)	Resistance (Ω/km)	Max Current (A)
AWG (solid)	Inches	mm	Circular Mil Area	Weight (lbs/1000 ft)	Weight (kg/km)	Resistance (Ω/1000 ft)	Resistance (Ω/km)	Max Current (A)
40	0.003145	0.07988	9.888	0.0299	0.0445	1049	3442	0.09
39	0.003531	0.08969	12.47	0.0377	0.0562	832	2729	0.11
38	0.003965	0.1007	15.72	0.0476	0.0708	660	2164	0.13
37	0.004453	0.1131	19.83	0.0600	0.0893	523	1716	0.17
36*	0.005000	0.1270	25.00	0.0757	0.113	415	1361	0.21
35	0.005614	0.1426	31.52	0.0954	0.142	329	1079	0.27
34	0.006304	0.1601	39.75	0.120	0.179	261	856	0.33
33	0.007080	0.1798	50.13	0.152	0.226	207	679	0.43
32	0.007950	0.2019	63.21	0.191	0.285	164	538	0.53
31	0.007950	0.2268	79.70	0.241	0.359	130	427	0.7
30	0.01003	0.2548	100.5	0.304	0.453	103	339	0.86
29	0.01126	0.2860	126.7	0.384	0.571	81.8	268	1.2
28	0.01246	0.3211	159.8	0.484	0.720	64.8	213	1.4
27	0.01419	0.3604	201.5	0.610	0.908	51.5	169	1.7
26	0.01594	0.4049	254.1	0.769	1.14	40.8	134	2.2
25	0.01790	0.4547	320.4	0.970	1.44	32.4	106	2.7
24	0.02010	0.5105	404.0	1.22	1.82	25.7	84.2	3.5
23	0.02257	0.5733	509.5	1.54	2.29	20.4	66.8	4.7
22	0.02535	0.6439	642.4	1.95	2.89	16.1	53.0	7
21	0.02846	0.7229	810.1	2.45	3.65	12.8	42.0	9
20	0.03196	0.8118	1022	3.09	4.60	10.2	33.3	11
19	0.03589	0.9116	1288	3.90	5.80	8.05	26.4	14
18	0.0403	1.024	1624	4.92	7.32	6.39	20.9	16
17	0.04526	1.150	2048	6.20	9.23	5.06	16.6	19
16	0.05082	1.291	2583	7.82	11.6	4.02	13.2	22
15	0.05707	1.450	3257	9.86	14.7	3.18	10.4	28
14	0.06408	1.628	4107	12.4	18.5	2.53	8.28	32
13	0.07196	1.828	5178	15.7	23.3	2.00	6.57	35
12	0.08081	2.053	6530	19.8	29.4	1.59	5.21	41
11	0.09074	2.305	8234	24.9	37.1	1.26	4.13	47
10	0.1019	2.588	10380	31.4	46.8	0.999	3.28	55
9	0.1144	2.906	13090	39.6	59.0	0.792	2.60	64
8	0.1285	3.264	16510	50.0	74.4	0.628	2.06	73
7	0.1443	3.665	20820	63.0	93.8	0.498	1.63	89
6	0.1620	4.115	26250	79.5	118	0.395	1.30	101
5	0.1819	4.620	33100	100	149	0.313	1.03	118
4	0.2043	5.189	41740	126	188	0.249	0.815	135
3	0.2294	5.827	52640	159	237	0.197	0.646	158
2	0.2576	6.543	66370	201	299	0.156	0.512	181
1	0.2893	7.348	83690	253	377	0.124	0.407	211
0	0.3249	8.252	105500	320	475	0.098	0.323	328
00	0.3648	9.266	133100	403	599	0.078	0.256	283
000	0.4096	10.40	167800	508	756	0.062	0.203	245
0000*	0.4600	11.68	211600	641	953	0.049	0.161

Wire Gauge Conversions to Diameter in Inches

All Units Are in Inches

GAUGE #	AWG	W & M	SWG	BWG	U.S. Standard
7/0	0.6513	0.490	0.500		0.5000
6/0	0.5800	0.460	0.464		0.4688
5/0	0.5165	0.430	0.432		0.4375
4/0	0.4600	0.3938	0.400	0.454	0.4063
3/0	0.4096	0.3625	0.372	0.425	0.3750
2/0	0.3648	0.3310	0.348	0.380	0.3438
1/0	0.3249	0.3065	0.324	0.340	0.3125
1	0.2893	0.2830	0.300	0.300	0.2813
2	0.2576	0.2625	0.276	0.284	0.2656
3	0.2294	0.2437	0.252	0.259	0.2391
4	0.2043	0.2253	0.232	0.238	0.2242
5	0.1819	0.2070	0.212	0.220	0.2092
6	0.1620	0.1920	0.192	0.203	0.1943
7	0.1443	0.1770	0.176	0.180	0.1793
8	0.1285	0.1620	0.160	0.165	0.1644
9	0.1144	0.1483	0.144	0.148	0.1495
10	0.1019	0.1350	0.128	0.134	0.1345
11	0.0907	0.1205	0.116	0.120	0.1196
12	0.0808	0.1055	0.104	0.109	0.1046
13	0.0719	0.0915	0.092	0.095	0.0897
14	0.0641	0.0800	0.080	0.083	0.0747
15	0.0571	0.0720	0.072	0.072	0.0673
16	0.0508	0.0625	0.064	0.065	0.0598
17	0.04526	0.054	0.056	0.058	0.0538
18	0.04030	0.0475	0.048	0.049	0.0478
19	0.03589	0.0410	0.040	0.042	0.0418
20	0.03196	0.0348	0.036	0.035	0.0359
21	0.02846	0.03175	0.032	0.032	0.0329
22	0.02535	0.0286	0.028	0.028	0.0299
23	0.02257	0.0258	0.024	0.025	0.0269
24	0.02010	0.0230	0.022	0.022	0.0239
25	0.01790	0.0204	0.020	0.020	0.0209
26	0.01594	0.0181	0.018	0.018	0.0179
27	0.01420	0.0173	0.0164	0.016	0.0164
28	0.01264	0.0162	0.0148	0.014	0.0149
29	0.01126	0.0150	0.0136	0.013	0.0135
30	0.0103	0.014	0.0124	0.012	0.0120
31	0.00893	0.0132	0.0116	0.010	0.0109
32	0.00795	0.0128	0.0108	0.009	0.0102
33	0.00708	0.0118	0.0100	0.008	0.0094
34	0.00630	0.0104	0.0092	0.007	0.0086
35	0.00561	0.0095	0.0084	0.005	0.0078
36	0.00500	0.0090	0.0076	0.004	0.0070
37	0.00445	0.0085	0.0068
38	0.00396	0.0080	0.0060
39	0.00353	0.0075	0.0052
40	0.00314	0.007	0.0048
41	0.00279	0.0066	0.0044
42	0.00249	0.0062	0.0040
43	0.00221	0.0060	0.0036
44	0.00198	0.0058	0.0032
45	0.00176	0.0055	0.0028
46	0.00157	0.0052	0.0024
47	0.00140	0.0050	0.0016
48	0.00124	0.0048	0.0012
49	0.00111	0.0046	0.0010
50	0.00099	0.0044
51	0.00088
52	0.00078
53	0.00070
54	0.00060
55	0.00050
56	0.00040
AWG = American Wire Gauge (Brown & Sharpe) W & M = Washburn & Moen (steel wire gauge) SWG = Imperial Standard Wire Gauge BWG = Birmingham or Stubs Wire Gauge US Standard = United States Standard (Revised)

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