Einstein's radius of universe, usually denoted in cosmology by RE, is the radius of curvature of space of Einstein's universe.

The exact length of Einstein's radius of universe is $R_E=c/\sqrt{4\pi G \rho}$, where where c is speed of light in vavcuum, G is Newtonian gravitational constant, and ρ is density of space.

Assuming that we live in stationary (neither expanding nor contracting) Einstein's universe in which the Hubble constant is ca. Ho = 70km / s / Mpc as established by observations, the Einstein's radius of universe is ca. 13 bilion light years. The exact number is then RE = c / Ho.