List of urban areas by population

This is a list of contiguous urban areas of the world ordered according to population as of 2011. The figures here have been compiled by Demographia.

Definitions and issues
Demographia defines an urban area (urbanized area agglomeration or urban centre) as a continuously built up landmass of urban development containing a high population density, without regard for administrative boundaries (i.e. municipality, city or commune) or a labor market (i.e. metropolitan area). Except in Australia, the authorities use a minimum urban density definition of 400 persons per square kilometer (or the nearly identical 1,000 per square mile in the United States). Demographia uses maps, satellite photographs to estimate continuous urbanization. Demographia also uses small area population data, where available, to match population estimates to urbanized land area. National census authority data are presented in Australia, Canada, France, Norway, Sweden, the United Kingdom and the United States. Census of India urban agglomerations are not used because the geographical size of constituent units (municipalities) often includes large rural (non-urban) areas.

Sources for population estimates and land area definitions are coded by letter in the Table below, respectively.
 * A: National census authority data for agglomerations (land area or population).
 * B: Demographia land area estimate based upon map or satellite photograph analysis.
 * C: Demographia "local area build up" population estimate from national statistical agency data.
 * D: Population estimate based upon the United Nations agglomeration estimate.
 * E: Demographia population estimate from national census authority metropolitan area data.
 * F: Other Demographia population estimate, such as from unofficial local reports.
 * H: Combination of adjacent national census authority agglomerations (land area or population).
 * L: Local government population estimate.

The most reliable population estimates are A and H. Population estimates C are generally reliable. Population estimates D are less reliable, because it is sometimes difficult to determine whether the data is based upon metropolitan area, urban area populations or some other definition. Population estimates E are also less reliable, for generally these estimates are derived by subtracting estimated population for the rural parts of metropolitan areas based upon estimated urban versus rural population differentials. Population estimates coded F and L are the least reliable (e.g. Beijing, Dongguan, Shanghai, Shenzhen, Suzhou and Quanzhou in the People's Republic of China, Bandung and Surabaya in Indonesia, and Tunis in Tunisia).

The projected year (2011) population estimate is further calculated from the base year population estimate using population growth rate based upon the United Nations 2007 World Urbanization growth rate with some exceptions.

The estimates are quite different from the list of World's largest urban agglomerations produced by the United Nations that reports inconsistently on urban geographic, despite its reference to agglomerations. This is evident, for example, in Manila, Kuala Lumpur, Jakarta, Seoul and Moscow, where the UN data are for political jurisdictions, rather than urban areas. In other cases, the UN data is for metropolitan area, which are larger than urban areas (such as in Brazil). Finally, the United Nations data is incomplete, excluding some significant urban areas (such as Essen–Düsseldorf in Germany or Pattaya in Thailand).

Urban areas are confined to a single metropolitan area or labor market area. In some cases, urban areas have virtually grown together (e.g. Taiheiyō Belt in Japan, the Pearl River Delta in the People's Republic of China and the Northeast megalopolis in the United States), yet are still considered separate urban areas. Urban areas that seem likely to grow together in the near future are also not combined (such as Dhaka and Narayanganj in Bangladesh or Tehran and Karaj in Iran).

Urban areas are confined to a single nation, unless there is freedom of movement (including labor) between the adjacent nations. Currently, this condition is met only between some continental nations of the European Union and Switzerland (e.g. Lille–Kortrijk in both France and Belgium, Aachen–Vaals in both Germany and Netherlands, Saarbrücken–Forbach in both Germany and France, and Geneva–Annemasse in both Switzerland and France). Thus, Detroit–Windsor in both the United States and Canada, and San Diego–Tijuana in both the United States and Mexico are not treated as single urban areas. Moreover, Shenzhen–Hong Kong in China is treated as separate urban areas, principally because labor movement between the two is limited.

According to the report, there are 796 identified urban areas in the world with 500,000 or more population as of 2011. As better satellite imagery has become available for a number of urban areas since the 2010 edition, this has resulted in land area increases or decreases in various urban areas, especially in Bangladesh, China and India. It is important to recognize that most of the data is estimated. Appropriate caution is therefore advised. Substantial population revisions are likely within the next two years as complete results are obtained for recent censuses in the People's Repulic of China, India, Japan and the United States.