(4) per square kilometre Explanation: For humans, population density is the number of people per unit of area usually per square kilometer or mile (which may include or exclude cultivated or potentially productive area). Commonly this may be calculated for a county, city, country, another territory, or the entire world. The world's population is 7 billion, and Earth's total area (including land and water) is 510 million square kilometers (197 million square miles. According to 2011 census population density of India is 382.