  We construct high signal-to-noise "template" spectra by co-adding hundreds of
spectra of nearby dwarfs spanning K7 to M4, taken with Keck/HIRES as part of
the California Planet Search. We identify several spectral regions in the
visible (370 - 800 nm) that are sensitive to the stellar luminosity and
metallicity. We use these regions to develop a spectral calibration method to
measure the mass, metallicity, and distance of low-mass stars, without the
requirement of geometric parallaxes. Testing our method on a sample of nearby M
dwarfs we show that we can reproduce stellar masses to about 8 - 10%,
metallicity to ~0.15 dex and distance to 11%. We were able to make use of HIRES
spectra obtained as part of the radial velocity monitoring of the star KOI-314
to derive a new mass estimate of 0.57 +/- 0.05 Msun, a radius of 0.54 +/- 0.05
Rsun, a metallicity, [Fe/H], of -0.28 +/- 0.10 and a distance of 66.5 +/- 7.3
pc. Using HARPS archival data and combining our spectral method with
constraints from transit observations, we are also able to derive the stellar
properties of GJ3470, a transiting planet hosting M dwarf. We estimate a mass
of 0.53 +/- 0.05 Msun, a radius of 0.50 +/- 0.05 Rsun, a metallicity, [Fe/H] =
0.12 +/- 0.12 and a distance of 29.9_{-3.4}^{+3.7} pc.
