The The Size of this Universe – from Śrīmad-Bhāgavatam 3.11.40-42 

SB 3.11.40—This phenomenal material world is expanded to a diameter of four billion miles, as a combination of eight material elements transformed into sixteen further categories, within and without, as follows.

The analytical studies of the material world are the subject matter of Sāṅkhya philosophy. The first sixteen diversities are the eleven senses and five sense objects, and the eight elements are the gross and subtle matter, namely earth, water, fire, air, sky, mind, intelligence and ego. All these combined together are distributed throughout the entire universe, which extends diametrically to four billion miles. Besides this universe of our experience, there are innumerable other universes. Some of them are bigger than the present one, and all of them are clustered together under similar material elements as described below.

SB 3.11.41—The layers or elements covering the universes are…