The Earth is HUGE, and there are a lot of us living here, but if everyone chose to live as densely as the population of Manhattan, the whole human race, right now, could fit into New Zealand.

There are 7.1 billion people on Earth.

New Zealand’s area is 103,738 square miles.

Manhattan’s population density is 70,517 people per square mile.

7,100,000,000 people / 103,738 sq mi in New Zealand = a density of 68,441 people/sq mi.

It would actually be less dense than Manhattan.

(Fact via waitbutwhy.com) and https://en.wikipedia.org/wiki/World_population