Volume of the Universe in Cubic Miles
In 10²¹, the diameter of the universe is placed at 2 x 10²³ miles. Its radius is half that, about 1 x 10²³ or simply, 10²³.

The formula for the volume of a sphere is 4/3Πr³.

Plugging in the radius of the universe into this formula gives:
(4/3) x 3.14 x 10²³ x 10²³ x 10²³
which is equal to
4.2 x 10⁶⁹.