  We report on preliminary results from the calculations of the QCD equation of
state for 2+1+1 flavors using HISQ action. The calculations are performed on
lattices with temporal extents $N_{\tau}=6,~8,~10$, and $12$ and aspect ratio
$N_{\sigma}/N_{\tau}=4$. We find that there is a significant contribution to
the pressure from charm quarks at temperatures $T> 300$ MeV.

High Energy Physics - Lattice;High Energy Physics - Phenomenology;Nuclear Theory