If the entire world population, which is nearly seven billion, was settled as densely as New York City, it could fit in an area equivalent to the size of Texas!
Of course living conditions would be nowhere near close to current US guidelines. As the population continues to grow, overpopulation is beginning to be a problem in places like India and China, which together hold over two billion people. Texas currently has around twenty-five million people living there. Just think what a stretch 7,000,000,000 would be!