The largest continent in the world, both in terms of space and population, is Asia. It takes up over 17 million square miles (44 million square kilometers), and is home to an estimated 3.8 billion people (3.800.000.000) — that's almost 60% of the entire world's population!
To compare, North America is a little over 9 million square miles (about 24 square kilometers) and has an estimated population of 529 million people. That means there are 7 times more people living in Asia than in North America.
Another method of determining how "big" a country or continent is by measuring its "population density" — that is, taking the number of people who live in a country and dividing it by the number of square miles or kilometers the country occupies. For example, if a group of 30 people lived on a 6 square kilometer patch of land, you would say that the land had a density of five people per square kilometer (even if there weren't exactly five people on each square kilometer!).
The city of Mumbai, which is the capital of India, is considered to be the most densely populated in the world, with over 29,000 people per square kilometer! In comparison, New York City has a population density of 10,500 people per square kilometer.