When the diameter of a wire is doubled, the AWG will decrease by 6. (e.g. No. 2 AWG is about twice the diameter of No. 8 AWG.)
When the area of a wire is doubled, the AWG will decrease by 3. (e.g. Two No. 14 AWG wires have about the same cross-sectional area as a single No. 11 AWG wire.)