And if you took each atom of all the humans alive and stacked them in a line (assuming 1 angstrom per atom and 7E17 atoms in a human), it would be roughly 60 light years long.
Late reply but my original numbers were wrong, it’s 7E27 atoms in a human according to wolfram, I think I just misinterpreted its original output when I tried to put it all in one formula: https://www.wolframalpha.com/input?i=how+many+atoms+in+a+hum...
The answer is still close to 60 LY (73.99LY) but it changes the cube size significantly:
915 square feet is still enough for some solar cells, a bio digester, an aquaponics setup with vegetable garden, a cabinet full of quail, a cot, a rocket stove, and a small shed.
And yet all humans alive, if packed like sardines, will fit in a 1 mile cube, with room to spare.
Physical dimensions can be an amazing un-intuitive thing.