Determining the world’s largest urban areas isn’t as cut and dry as it may seem to the casual reader. Not all countries and accounting agencies use the same criteria when determining the population of a particular city and its metropolitan area. Additionally, not all cities have precisely-defined boundaries and that can also make determining its landmass and population difficult.

One fine example where varying methods come into play can be the case of Tokyo. As I discussed in an earlier topic, the Japanese government does not recognize Tokyo as a city as most foreigners do and therefore, there are no real city boundaries with which most international accounting agencies can use in determining the population of the entire urban region. Therefore, although almost all accounting agencies will agree that Tokyo is the world’s largest metropolitan area, its population has varied from as low as 26 million to as high as 40 million depending on the agency reporting its population.

This case can also be extended to many cities in China. The four Chinese cities on the list, as well as Bangkok and Seoul, are actually merged with their entire municipalities and have no data that indicate inner-city populations.

Because of the differences in determining where a city’s urban area boundaries end, the populations of many of the listed urban areas below have varied in other texts and lists. Chicago’s population has been listed in some texts at just 7.2 million while some have determined it to be as high as 12 million. And while many agencies consider Los Angeles, Orange, Ventura, Santa Barbara, San Bernardino and Riverside Counties to be part of Los Angeles’ metropolitan area, which would give it a population of roughly 18 million, others have determined that only Los Angeles, Orange and Ventura Counties to be part of the urban area, resulting in a population of just over 13 million.

1. Tokyo – Population: 35.3 million, Country: Japan, First settled: 1457

2. Seoul – Population: 24.6 million, Country: South Korea, First settled: 1394

3. Mexico City – Population: 23.7 million, Country: Mexico, First settled: 1325

4. New York City – Population: 21.8 million, Country: USA, First settled: 1625

5. Moscow – Population: 21.2 million, Country: Russia, First settled: 1147

6. Shanghai – Population: 20.4 million, Country: China, First settled: c.960

7. Rio de Janeiro – Population: 19.6 million, Country: Brazil, First settled: 1502

8. Sao Paulo – Population: 18.5 million, Country: Brazil, First settled: 1554

9. Beijing – Population: 17.8 million, Country: China, First settled: c.2000 B.C.

10. Mumbai – Population: 17.4 million, Country: India, First settled: c.1530

11. Osaka – Population: 17 million, Country: Japan, First settled: 900’s

12. Calcutta – Population: 16.7 million, Country: India, First settled: 1690

13. Los Angeles – Population: 16.2 million, Country: USA, First settled: 1781

14. Chongching – Population: 15.6 million, Country: China, First settled: c.3000 B.C.

15. London – Population: 15.1 million, Country: UK, First settled: A.D. 43

16. Delhi – Population: 14.6 million, Country: India, First settled: 1600’s

17. Guangzhou – Population: 14 million, Country: China, First settled: 214 B.C.

18. Karachi – Population: 13.3 million, Country: Pakistan, First settled: 1729

19. Bangkok – Population: 12.4 million, Country: Thailand, First settled: c.1350

20. Cairo – Population: 11.6 million, Country: Egypt, First settled: c.3100 B.C.

21. Tehran – Population: 11.1 million, Country: Iran, First settled: c.2000 B.C.

22. Paris – Population: 10.8 million, Country: France, First settled: 52 B.C.

23. Manila – Population: 10.6 million, Country: Philippines, First settled: 1571

24. Chicago – Population: 10.2 million, Country: USA, First settled: 1770’s

25. Lagos – Population: 10 million, Country: Nigeria, First settled: 1472