Holy Terra’s population (Warhammer 40k)
Earth has a surface area of 510,072,000 square kilometers (assuming you get rid of the pesky oceans and turn the entire surface into city)
The Kowloon Walled City had a population density of 1,300,000 people per square kilometer, the highest population density on Earth. This translates to 660 TRILLION people on a planet.
I did some cursory googling and found an excerpt that says Terra has a population in the quadrillions. Assuming 15 quadrillion people is 29,370,300 person/square kilometer.
Which is roughly 20x the pop density of Kowloons.
HOWEVER
Terra is a planet city that’s been developed and built up for millennia. It likely has been built upwards and downwards, effectively increasing its housing area. So if it has tower hab blocks and sky scrapers, I can see quadrillions work out. Naturally, it would have horrific waste management issues, and many would starve on a regular basis due to logistics problems, but since when has the Imperium cared? Life is cheap.
