Simply stated, AWG or American wire gauge is the standard system that determines a cross section of a wire using a gauge for solid, round electrical wires. The higher the AWG number, the thinner or smaller the wire. Used since 1857, AWG has helped users determine a wire’s current-carrying ratings.
AWG is determined by figuring out the radius of the wire squared, times pi. Most often, we use the term “circular mil,” which is the area of a 1/1000 or 1 mil diameter circle. These measurements are made on the wire alone; no jacketing or insulation factors into AWG size.
AWG relates also to resistance; so a thicker wire has less resistance and thus can carry more voltage a longer distance.
When stranding conductors, it is common to use smaller gauge sizes with higher AWG numbers, as they are more flexible and durable during applications that experience bending and vibrations. And although you can tightly braid or wind wires, there will always be a small gap between each strand, so stranded AWG wires are always slighter bigger in diameter than their solid wire counterparts.
AWG tables are only for single, round conductors. A conversion table is required for stranded conductors. Most cable providers provide AWG data on their spec sheets.