[cromulent]

You can fit all the humans on earth into a 1km cube.

Average volume of a human is 66l [1]. Make it 130l to allow some unused space due to imperfect packing.

7.6 billion * 130l = 988 000 000 000 liters.

1 cubic kilometer = 1 000 000 000 000 liters.

[1] https://www.wolframalpha.com/input/?i=average%20volume%20of%...

[Simon_says]

You wouldn't enjoy it.

[garmaine]

A better reference: https://what-if.xkcd.com/4/

"What would happen if you were to gather a mole (unit of measurement) of moles (the small furry critter) in one place?"