AWG is a older way of doing the exact same thing as our metric wire sizes do. It's a geometric series where five steps makes the cross sectional area ten times larger, i.e. 6 AWG is ten times larger than 16 AWG just like 16 mm2 is ten times larger than 1.5 mm2. (Only every other size is used in AWG) Take five metric steps and you go 1.5; 2.5; 4; 6; 10; 16. The AWG does the same thing, but as the series used is an approximation the actual steps differ slightly from those used for the metric sizes. Both series use rounded numbers and the manufacturers on both sides of the Atlantic allow for fairly wide tolerances when making wires.
