To determine effective 60-Hertz ac resistance, multiply dc resistance values
corrected for proper temperature, by the ac/dc resistance ratio given below. These
apply to the following specific conditions. 
     Use Columns 1 and 2 for: 
     (a) Single-conductor non-metallic sheathed cables — in air or non-metallic
     conduit.
     (b) Single-conductor metallic-sheathed cables with sheaths insulated — in air or
     separate non-metallic conduits.
     (c) Multiple-conductor non-metallic sheathed cables — in air or non-metallic
     conduits.

Note: Columns 1 and 2 include skin effect only. For close spacing such as
multi-conductor cables or several cables in the same conduit, there will be an
additional apparent resistance due to proximity loss. This varies with spacing
(insulation thickness) but for most purposes can be neglected without serious error.
     Use Column 3 for:
     (a) Multiple-conductor metallic-sheathed cable.
     (b) Multiple-conductor non-metallic sheathed cables in metal conduit.
     (c) Two or more single-conductor non-metallic sheathed cables in same metallic
     conduit. 

ac/dc resistance ratios
for copper and aluminum
conductors 60 Hertz (65°C) 

Conductor
Size AWG
or kcmil 

1
Standard Conductor 

2
Segmental Conductor 

3
All Strandings 

Copper 

Aluminum 

Copper 

Aluminum 

Copper 

Aluminum 

Up to 3
2 and 1
 0

1.000
1.000
1.001

1.000
1.000
1.000

—
—
—

—
—
— 

1.00
1.01
1.02

1.00
1.00
1.00

00
000
0000

1.001
1.002
1.004

1.001
1.001
1.001

—
—
—

—
—
— 

1.03
1.04
1.05

1.00
1.01
1.01

250
300
350

1.005
1.006
1.009

1.002
1.003
1.004

—
—
—

—
—
— 

1.06
1.07
1.08

1.02
1.02
1.03

400
500
600

1.011
1.018
1.025

1.005
1.007
1.010

—
—
—

—
—
— 

1.10
1.13
1.16

1.04
1.06
1.08

700
750
800

1.034
1.039
1.044

1.013
1.015
1.017

—
—
—

—
—
— 

1.19
1.21
—

1.11
1.12
1.14

1000
1250
1500

1.067
1.102
1.142

1.026
1.040
1.058

1.010
1.018
1.028

1.005
1.008
1.012

—
—
—

1.19
1.27
—

1750
2000
2500

1.185
1.233
1.326

1.079
1.100
1.142

1.038
1.052
1.078

1.016
1.020
1.028

—
—
—

—
—
—