  We derive expressions for the Ricci curvature tensor and scalar in terms of
intrinsic torsion classes of half-flat manifolds by exploiting the relationship
between half-flat manifolds and non-compact $G_2$ holonomy manifolds. Our
expressions are tested for Iwasawa and more general nilpotent manifolds. We
also derive expressions, in the language of Calabi-Yau moduli spaces, for the
torsion classes and the Ricci curvature of the \emph{particular} half-flat
manifolds that arise naturally via mirror symmetry in flux compactifications.
Using these expressions we then derive a constraint on the K\"ahler moduli
space of type II string theories on these half-flat manifolds.
