If all the people in the world were in one place, how much area would it take up.

We have 7 billion people in the world which is 7,000,000,000 people.  If one person took up 1 square metre each, the entire world population would take up only 7,000 square kilometres.

That would be the about the size of Puerto Rico or Haiti.

Haiti - Just over 7,000 square kilometres

The world land area is about 149 million km2, so every person could have about 20,000 square metres each.  Does not sound like overpopulation just yet.

Also with the rate of increase slowing the world population will peak sometime this century and then start reversing.  So no real threat. Nothing really to worry about.

 To read more see here.