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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 gauge). It has been in existence since the mid 1800s in the U.S. and Canada.

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

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.

A circular mil is the cross-sectional area of a circle with a diameter of 1 mil (1/000th of an inch).

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)
Inches mm
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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