dc Resistance (2)
Based on the resistance-temperature
coefficient of copper of 100 percent
conductivity and of aluminum 61 per-
cent conductivity (international an-
nealed copper standard) at 25°C and
the formulas:
R1 = Resistance at 25°C
R2 = Resistance at desired temp. T
2  T1 = 25°C

Copper        
R
2 = R1  


dc resistance eq



Example:
 
R dc at 75°C for 4/0 AWG
uncoated copper = 0.0509x
1.193 = .0607 ohms/1000ft. 

Aluminum 
R
2 = R1  

dc_resistance eq 2
Resistance temperature correction factors
Copper Conductors

Temp. C 

0
10
20

.904
.942
.981

.908
.946
.985

.911
.950
.988

.915
.954
.992

.919
.958
.996

.923
.961
1.000

.927
.965
1.004

.931
.969
1.008

.934
.973
1.012

.938
.977
1.015

30
40
50

1.019
1.058
1.096

1.023
1.062
1.100

1.027
1.066
1.104

1.031
1.069 1.108

1.035
1.073
1.111 

1.039
1.077
1.115

1.042
1.081
1.119

1.046
1.085
1.123

1.050
1.089
1.127

1.054
1.092
1.131

60
70
80

1.135
1.173
1.212

1.139
1.177
1.216

1.143
1.181
1.220

1.146
1.185
1.224

1.150
1.189
1.227

1.154
1.193
1.231

1.158
1.197
1.235

1.162
1.200
1.239

1.166
1.204
1.243

1.170
1.208
1.247

90
100
110

1.250
1.289
1.328

1.254
1.293
1.331

1.258
1.297
1.335

1.262
1.300
1.339

1.266
1.304
1.343

1.270
1.308
1.347

1.274
1.312
1.351

1.277
1.316
1.354

1.281
1.320
1.358

1.285
1.324
1.362

120
130
140

1.366
1.405
1.443

1.370
1.408
1.447

1.374
1.412
1.451

1.378
1.416
1.455

1.381
1.420
1.459

1.385
1.424
1.462

1.389
1.428
1.466

1.393
1.432
1.470

1.397
1.435
1.474

1.400
1.439
1.478

150

1.482

1.480

1.489

1.493

1.497

1.500

1.505

1.509

1.513

1.516

 

Aluminum Conductors

Temp. C 

0
10
20

.901
.940
.980

.905
.944
.984

.909
.948
.988

.913
.952
.992

.917
.956
.996

.921
.960
1.000

.925
.964
1.004

.928
.968
1.008

.932
.972
1.012

.936
.976
1.016

30
40
50

1.020
1.060
1.100

1.024
1.064
1.104

1.028
1.068
1.108

1.032
1.072 1.112

1.036
1.076
1.116

1.040
1.080
1.120

1.044
1.084
1.124

1.048
1.088
1.128

1.052
1.092
1.132

1.056
1.096
1.136

60
70
80

1.140
1.180
1.219

1.144
1.184
1.223

1.148
1.187
1.227

1.152
1.191
1.231

1.156
1.195
1.235

1.160
1.199
1.239

1.164
1.203
1.243

1.168
1.207
1.246

1.172
1.211
1.250

1.176
1.215
1.254

90
100
110

1.258
1.297
1.336

1.262
1.301
1.340

1.266
1.304
1.343

1.270
1.308
1.347

1.274
1.311
1.351

1.278
1.315
1.355

1.281
1.319
1.359

1.285
1.324
1.362

1.289
1.328
1.366

1.293
1.332
1.370

120
130
140

1.374
1.413
1.452

1.378
1.417
1.456

1.381
1.420
1.459

1.385
1.424
1.463

1.389
1.428
1.467

1.393
1.432
1.471

1.397
1.436
1.475

1.401
1.440
1.479

1.405
1.444
1.483

1.409
1.448
1.487

150

1.491

1.495

1.498

1.502

1.506

1.510

1.514

1.518

1.522

1.526