How To Measure Speaker Wire Size. Most speaker manufacturers list an impedance rating on the speaker label or the packaging. This is why the thinest wire has the largest number.
In this case, it's usually best to follow the advice of the borg resistance is futile. American wire gauge (awg) is a standardized system established in 1857 used to measure the diameter of wires. There are a lot of ways to measure a speaker wire size.
Originaly the gauge represented the number of holes the wire had to be drawn through.
Determine the gauge of the outdoor speaker wire needed. Specifically for speaker wire, the most common gauges available are 12, 14, 16 and 18. (yes, 10awg would be even thicker, but then you start running into other problems with. If unsure what size, measure the speaker wire tabs with a ruler.