Aug 31, 2016

$6 \cdot {10}^{51} k g$

Explanation:

A total mass of the visible matter of about $6 \cdot {10}^{51} k g$

The mass density of visible matter (i.e., galaxies) in the Universe is estimated at 3*10^-28 (kg)/m^3^. The radius of the visible Universe is estimated at $1.7 \cdot {10}^{26} m$. Plus or minus 20 percent. Therefore, you can compute the mass of the universe.