  We have analyzed the retrieval of the relation between mass and absolute Gaia
G magnitude as obtained from theoretical models by \cite{2012MNRAS.427..127B}
for the stars of different luminosity classes. For subgiant and main-sequence
stars, we provide approximate analytical direct and inverse relations based on
the most probable value of G magnitude in the course of evolution within the
given stage. A comparison with (albeit few) observational data confirms that
our results can be used for the estimation of the stellar mass from Gaia
photometry in the range of 1 to 10 solar mass. We argue that similar relations
for other luminosity classes are not informative.
