  We present exact results for the electronic transport properties of graphene
sheets connected to two metallic electrodes. Our results, obtained by
transfer-matrix methods, are valid for all sheet widths and lengths. In the
limit of large width-to-length ratio relevant to recent experiments, we find a
Dirac-point conductivity of $2e^2/\sqrt{3}h$ and a sub-Poissonian Fano factor
of $2 - 3\sqrt{3}/\pi \simeq 0.346$ for armchair graphene; for the zigzag
geometry these are respectively 0 and 1. Our results reflect essential effects
from both the topology of graphene and the electronic structure of the leads,
giving a complete microscopic understanding of the unique intrinsic transport
in graphene.
