The average population density was calculated from the total global population (6,000,000,000) and the total surface area of the Earth. As about 70% of the Earth's surface is covered with water, land area is a better value to use.
If only total land area is considered, the average global density is 40.3 people per square kilometer. However not all land is equally suitable for human habitation. The land surface can be divided into different types:
- land which is permanently covered in snow or ice - 20%
- Mountains - 20%
- Desert - 20%
- Land without topsoil eg bare rock - 10%
- Arable land (land which can be farmed) - 30%
Using only arable land, the average population density is 134.4 people per square kilometer. Although this appears to be a large number, a crowded beach is estimated to be 250,000 - 300,000 people per square kilometer.
Population is seldom evenly distributed throughout any country. Typically in countries with a high level of urbanisation, a few major urban centres and several smaller urban areas will contain most of the population.
Countries with high population densities have very small land areas and most of these are island nations.