Terry Pratchett said this quote

“ Few religions are definite about the size of Heaven, but on the planet Earth the Book of Revelation (ch. XXI, v.16) gives it as a cube 12,000 furlongs on a side. This is somewhat less than 500,000,000,000,000,000,000 cubic feet. Even allowing that the Heavenly Host and other essential services take up at least two thirds of this space, this leaves about one million cubic feet of space for each human occupant- assuming that every creature that could be called ‘human’ is allowed in, and the the human race eventually totals a thousand times the numbers of humans alive up until now. This is such a generous amount of space that it suggests that room has also been provided for some alien races or - a happy thought - that pets are allowed. ”