  We present a new direct spectroscopic calibration for a fast estimation of
the stellar metallicity [Fe/H]. These calibrations were computed using a large
sample of 451 solar-type stars for which we have precise spectroscopic
parameters derived from high quality spectra. The new [Fe/H] calibration is
based on weak Fe I lines, which are expected to be less dependent on surface
gravity and microturbulence, and require only a pre-determination of the
effective temperature. This temperature can be obtained using a previously
presented line-ratio calibration. We also present a simple code that uses the
calibrations and procedures presented in these works to obtain both the
effective temperature and the [Fe/H] estimate. The code, written in C, is
freely available for the community and may be used as an extension of the ARES
code. We test these calibrations for 582 independent FGK stars. We show that
the code can be used as a precise and fast indicator of the spectroscopic
temperature and metallicity for dwarf FKG stars with effective temperatures
ranging from 4500 K to 6500 K and with [Fe/H] ranging from -0.8 dex to 0.4 dex.
