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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
000000 (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:
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.
The IACS value of 58.0 MS/m is used as the conductivity of copper.
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.
A density of copper of 8920 kg/m3 is used to derive the mass
An allowance of 750 kcmil/A is generally sufficient for calculating current capacity. The more relaxed 500 kcmil/A is an absolute maximum.
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.
