Wire sizes: Wire Resistance Table
Summary: Different wire gauges have varying degrees of resistance.
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. The DC resistance presented is for Stranded Wire. ^{[1]}
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 1.25^{2} 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 Gauge and Resistance
The temperature all measurements (volume, length and resistance) were made at is 20º C. Figure shown is for stranded wire, DC resistance.
AWG Number |
Diameter, in Mils |
Ohms per thousand feet ^{[2]} |
---|---|---|
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 |
Solid Wire Resistance Compared to Stranded Wire
This table presents the DC resistance of Solid and Stranded wire of the same gauge. This topic often appears in discussions regarding DCC wiring and the advantages of using one type of wire construction over another.
Bear in mind that the value shown for stranded is a calculated average of several wires constructed of differing strand counts and wire gauge.
As demonstrated in the table, stranded wire often has less average resistance. In many applications, the advantages of stranded wire outweigh those of solid wires. As this is an average, some wires, due to their number of strands and gauge, could exhibit more resistance than the equivalent solid wire. Consult the manufacturer literature for an accurate value of a specific wire.
Resistance Solid Vs Stranded^{[3]}^{[4]} |
DC Ohms per Thousand Feet | |
---|---|---|
Solid | Stranded | |
22 | 16.8 | 14.8 |
20 | 10.5 | 9.8 |
18 | 6.6 | 6.5 |
16 | 4.2 | 4.0 |
14 | 2.6 | 2.5 |
12 | 1.7 | 1.65 |
10 | 1 | 1.04 |
8 | 0.67 | 0.62 |
6 | 0.47 | 0.40 |
- ↑ The resistance of a stranded wire is directly related to the gauge of the strands, and the number of strands used.
- ↑ DC Resistance for Stranded Wire
- ↑ The value shown for Stranded Wire is an average value, as there are multiple gauge/strand count wires offered.
- ↑ Taken from an Ideal Wire and Cable catalog.