12 AWG wire will be used with 20 amp circuits to provide a bit more power to kitchens, garages and outdoor lights. 30 amp circuits power larger appliances like water heaters and clothes dryers ...

and the AWG of a stranded conductor is that of a single solid round conductor with the same conductive cross-sectional area – so, as stranded cable has gaps between the strands, 20 AWG stranded ...