Laymans terms:

"1080p framebuffer using forward rendering and no AA at 32 bits per pixel would be ~24mb IIRC, however using deferred rendering which is far more likely would put it at the total of 2073600 pixels so at differing BPP(Bytes per pixel) we would get:

16 BPP: 31.64mb
20 BPP: 39.55mb
24 BPP: 47.46mb
28 BPP: 55.37mb
32 BPP: 63.28mb

As a reference BF3 (1080p on PC) is 20BPP and KZ:SF is 24BPP both without AA."