Practical Electronics/SWG

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The thickness of a wire is often given as a Standard Wire Gauge, or SWG. This is number from 0000000 or 7/0 (thickest) to 50 (thinnest). The gauge of most wire used in electronics is between 20 and 30. Often, a wire gauge will be stated followed by "swg", so 26 swg, etc.

It is very important that you do not confuse SWG with AWG, which means American Wire Gauge - although fairly similar, it is a different system of sizing wires.

The table below lists the SWG gauges, along with the diameter in inches and millimetres.

Standard Wire Gauge Diameter Turns of wire Cross-sectional area Res. per length (for copper wire) Mass per length Current Capacity / A
in mm in−1 mm−1 kcmil mm2 Ω/km Ω/kft lb/ft kg/m 750 kcmil/A 500kcmil/A
0000000 (7/0) 0.500 12.7 2.00 0.0787 250 127 0.136 0.447 0.759 1.13 333 500
000000 (6/0) 0.464 11.8 2.16 0.0848 215 109 0.158 0.519 0.654 0.973 287 431
00000 (5/0) 0.432 11.0 2.31 0.0911 187 94.6 0.182 0.598 0.567 0.844 249 373
0000 (4/0) 0.400 10.2 2.50 0.0984 160 81.1 0.213 0.698 0.486 0.723 213 320
000 (3/0) 0.372 9.45 2.69 0.106 138 70.1 0.246 0.807 0.420 0.625 185 277
00 (2/0) 0.348 8.84 2.87 0.113 121 61.4 0.281 0.922 0.368 0.547 161 242
0 (1/0) 0.324 8.23 3.09 0.122 105 53.2 0.324 1.06 0.319 0.474 140 210
1 0.300 7.62 3.33 0.131 90.0 45.6 0.378 1.24 0.273 0.407 120 180
2 0.276 7.01 3.62 0.143 76.2 38.6 0.447 1.47 0.231 0.344 102 152
3 0.252 6.40 3.97 0.156 63.5 32.2 0.536 1.76 0.193 0.287 84.7 127
4 0.232 5.89 4.31 0.170 53.8 27.3 0.632 2.07 0.163 0.243 71.8 108
5 0.212 5.38 4.72 0.186 44.9 22.8 0.757 2.48 0.137 0.203 59.9 89.9
6 0.192 4.88 5.21 0.205 36.9 18.7 0.923 3.03 0.112 0.167 49.2 73.7
7 0.176 4.47 5.68 0.224 31.0 15.7 1.10 3.60 0.0941 0.140 41.3 62.0
8 0.160 4.06 6.25 0.246 25.6 13.0 1.33 4.36 0.0778 0.116 34.1 51.2
9 0.144 3.66 6.94 0.273 20.7 10.5 1.64 5.38 0.0630 0.0937 27.6 41.5
10 0.128 3.25 7.81 0.308 16.4 8.30 2.08 6.81 0.0498 0.0741 21.8 32.8
11 0.116 2.95 8.62 0.339 13.5 6.82 2.53 8.30 0.0409 0.0608 17.9 26.9
12 0.104 2.64 9.62 0.379 10.8 5.48 3.15 10.3 0.0329 0.0489 14.4 21.6
13 0.0920 2.34 10.9 0.428 8.46 4.29 4.02 13.2 0.0257 0.0383 11.3 16.9
14 0.0800 2.03 12.5 0.492 6.40 3.24 5.32 17.4 0.0194 0.0289 8.53 12.8
15 0.0720 1.83 13.9 0.547 5.18 2.63 6.56 21.5 0.0157 0.0234 6.91 10.4
16 0.0640 1.63 15.6 0.615 4.10 2.08 8.31 27.3 0.0124 0.0185 5.46 8.19
17 0.0560 1.42 17.9 0.703 3.14 1.59 10.9 35.6 0.00952 0.0142 4.18 6.27
18 0.0480 1.22 20.8 0.820 2.30 1.17 14.8 48.5 0.00700 0.0104 3.07 4.61
19 0.0400 1.02 25.0 0.984 1.60 0.811 21.3 69.8 0.00486 0.00723 2.13 3.20
20 0.0360 0.914 27.8 1.09 1.30 0.657 26.3 86.1 0.00394 0.00586 1.73 2.59
21 0.0320 0.813 31.3 1.23 1.02 0.519 33.2 109 0.00311 0.00463 1.37 2.05
22 0.0280 0.711 35.7 1.41 0.784 0.397 43.4 142 0.00238 0.00354 1.05 1.57
23 0.0240 0.610 41.7 1.64 0.576 0.292 59.1 194 0.00175 0.00260 0.768 1.15
24 0.0220 0.559 45.5 1.79 0.484 0.245 70.3 231 0.00147 0.00219 0.645 0.968
25 0.0200 0.508 50.0 1.97 0.400 0.203 85.1 279 0.00121 0.00181 0.533 0.800
26 0.0180 0.457 55.6 2.19 0.324 0.164 105 345 984µ 0.00146 0.432 0.648
27 0.0164 0.417 61.0 2.40 0.269 0.136 127 415 817µ 0.00122 0.359 0.538
28 0.0148 0.376 67.6 2.66 0.219 0.111 155 510 665µ 990µ 0.292 0.438
29 0.0136 0.345 73.5 2.89 0.185 0.0937 184 604 562µ 836µ 0.247 0.370
30 0.0124 0.315 80.6 3.18 0.154 0.0779 221 726 467µ 695µ 0.205 0.308
31 0.0116 0.295 86.2 3.39 0.135 0.0682 253 830 409µ 608µ 0.179 0.269
32 0.0108 0.274 92.6 3.65 0.117 0.0591 292 957 354µ 527µ 0.156 0.233
33 0.0100 0.254 100 3.94 0.100 0.0507 340 1120 304µ 452µ 0.133 0.200
34 0.00920 0.234 109 4.28 0.0846 0.0429 402 1320 257µ 383µ 0.113 0.169
35 0.00840 0.213 119 4.69 0.0706 0.0358 482 1580 214µ 319µ 0.0941 0.141
36 0.00760 0.193 132 5.18 0.0578 0.0293 589 1930 175µ 261µ 0.0770 0.116
37 0.00680 0.173 147 5.79 0.0462 0.0234 736 2410 140µ 209µ 0.0617 0.0925
38 0.00600 0.152 167 6.56 0.0360 0.0182 945 3100 109µ 163µ 0.0480 0.0720
39 0.00520 0.132 192 7.57 0.0270 0.0137 1260 4130 82.1µ 122µ 0.0361 0.0541
40 0.00480 0.122 208 8.20 0.0230 0.0117 1480 4850 70.0µ 104µ 0.0307 0.0461
41 0.00440 0.112 227 8.95 0.0194 0.00981 1760 5770 58.8µ 87.5µ 0.0258 0.0387
42 0.00400 0.102 250 9.84 0.0160 0.00811 2130 6980 48.6µ 72.3µ 0.0213 0.0320
43 0.00360 0.0914 278 10.9 0.0130 0.00657 2630 8610 39.4µ 58.6µ 0.0173 0.0259
44 0.00320 0.0813 313 12.3 0.0102 0.00519 3320 10900 31.1µ 46.3µ 0.0137 0.0205
45 0.00280 0.0711 357 14.1 0.00784 0.00397 4340 14200 23.8µ 35.4µ 0.0105 0.0157
46 0.00240 0.0610 417 16.4 0.00576 0.00292 5910 19400 17.5µ 26.0µ 0.00768 0.0115
47 0.00200 0.0508 500 19.7 0.00400 0.00203 8510 27900 12.1µ 18.1µ 0.00533 0.00800
48 0.00160 0.0406 625 24.6 0.00256 0.00130 13300 43600 7.78µ 11.6µ 0.00341 0.00512
49 0.00120 0.0305 833 32.8 0.00144 730µ 23600 77500 4.37µ 6.51µ 0.00192 0.00288
50 0.00100 0.0254 1000 39.4 0.00100 507µ 34000 112000 3.04µ 4.52µ 0.00133 0.00200
Notes:
  1. All values are rounded to three significant figures. Values less than 1×10−6 are shown with appropriate SI prefixes to avoid a large number of leading zeros.
  2. The IACS value of 58.0 MS/m is used as the conductivity of copper.
  3. These calculations do not take into account AC effects such as the skin effect - perform suitable calculations before using in a high-frequency application. Grid mains frequencies (50-60 Hz) should not have a noticeable effect, as the skin depth is over 8mm.
  4. A density of copper of 8920 kg/m3 is used to derive the mass
  5. An allowance of 750 kcmil/A is generally sufficient for calculating current capacity. The more relaxed 500 kcmil/A is an absolute maximum.
  6. The values are guidelines − exact values will depend on the type of wire and operating conditions such as ambient temperature, thermal conductivity of the surroundings.

External links[edit]

the value under "current capacity/A" shown in the table as "750 kcmil/A" & "500 kcmil/A" should read as "750 cmil/A" & "500 cmil/A" instead. this can be checked by dividing any value under "area in kcmil" with 750 cmil/A or by 500 cmil/A the result in Current capacity column will match. it is not matching now. moreover the column "current capacity/A" should read as " current capacity in A".

The values for resistance in ohms per kft are not correct. They appear to have been derived from the figures for ohms per km, which are correct, by multiplying that figure by 3.28 (the conversion factor from metres to feet) rather than dividing by 3.28.