  We compute the moduli Kahler potential for M-theory on a compact manifold of
G_2 holonomy in a large radius approximation. Our method relies on an explicit
G_2 structure with small torsion, its periods and the calculation of the
approximate volume of the manifold. As a verification of our result, some of
the components of the Kahler metric are computed directly by integration over
harmonic forms. We also discuss the modification of our result in the presence
of co-dimension four singularities and derive the gauge-kinetic functions for
the massless gauge fields that arise in this case.
