# Wire Resistance Table

## American Wire Gauge

The following table gives the size of various conductors, with the diameter in Mils. One Mil is 0.001 inches, or one one-thousand of an inch.

The temperature all measurements (volume, length and resistance) were made at is 20º C.

It is worthwhile to note that cross-sectional dimensions are chosen such at each decrease in gauge number represents a 25% increase of the cross-sectional area. On this basis, a decrease of three gauge numbers will represent an increase of the cross-sectional area of 1.25 × 1.25 × 1.25, for an approximate increase of 2:1. Similarly a change of ten gauge numbers will represent approximately an 9:1 change in cross-sectional area.

Since doubling the cross-sectional area cuts the resistance in half, a decrease of three gauge numbers will decrease the resistance of a given length of wire by half.

Applying the rule of 1.25(Number of steps) allows for quick calculations for the increase or decrease in resistance between various wire gauges.

For example, AWG 22 has almost 9 times the resistance as that of 12 AWG (10 steps). Or 14 AWG has 1.252 or 1.6 times that of AWG 12's resistance.

Using that knowledge, a 10 foot run of AWG 14 is equivalent to 16 feet of AWG 12.

To calculate the approximate resistance of a wire, start with AWG 10 = 1Ω per thousand feet. Using the rule above will allow you to calculate the approximate resistance of any wire using the calculated multiplier. Example:

• 14AWG, 10 – 14 = 4 steps, 1.25^4 = 2.44

Therefore 14AWG is approximately 2.44Ω per thousand feet. (If you use 1.26^4 the result is closer at 2.52. The 1.25 factor is easier to remember.)

### Conductor Sizes

The temperature all measurements (volume, length and resistance) were made at is 20º C.

AWG
Number
Diameter,
in Mils
Ohms per
thousand feet
10 101.9 0.9989
11 90.74 1.260
12 80.81 1.588
13 71.96 2.003
14 64.05 2.525
15 57.07 3.184
16 50.82 4.016
17 45.26 5.064
18 40.30 6.385
19 35.89 8.051
20 31.96 10.15
21 28.46 12.80
22 25.35 16.14

### Recommended Wire Gauge Chart

Wire Gauge Guidelines for a DCC Power Bus
American Wire Gauge (AWG)
https://dccwiki.com/Wire_Sizes_and_Spacing
Scale G 0 S H0 00 TT N Z N−Trak
Ratio 1:20.3 1:29 1:48 1:64 1:87.1 1:76.2 1:120 1:160 1:220
Bus
Length
< 21 ft < 6m 12 14 14 16 16
21 − 40 6 − 12m 10 12 − 14 14 14
> 40 ft > 12m 8 12 12
Feeder Wire
Length
< 5 ft < 1.5M 16 18 − 22 20 18 − 22 18 − 22
< 10 ft < 3m 14 18 − 20 18 − 20 18 − 20
Recommended Wire Gauge
N−Trak is based on the N−Trak Wiring RP for DCC
http://ntrak.org/ntrak_powerpole_rp.htm