  In this paper, we formulate a new model of density distribution for halos
made of warm dark matter (WDM) particles. The model is described by a single
microphysics parameter - the mass (or, equivalently, the maximal value of the
initial phase-space density distribution) of dark matter particles. Given the
WDM particle mass and the parameters of a dark matter density profile at the
halo periphery, this model predicts the inner density profile. In case of
initial Fermi-Dirac distribution, we successfully reproduce cored dark matter
profiles from N-body simulations. Also, we calculate the core radii of warm
dark matter halos of dwarf spheroidal galaxies for particle masses
$m_\text{FD}=$100, 200, 300 and 400 eV.
