All population figures for the world's largest urban areas are simply estimates. There's no way to know the exact population of such a large place. If you don't like this list, you can review Largest Cities in the World - List Two, based on different methodologies. Both lists are valid estimates.
1. Tokyo-Yokohama, Japan - 33,200,000
2. New York, United States - 17,800,000
3. Sao Paulo, Brazil - 17,700,000
4. Seoul-Incheon, South Korea - 17,500,000
5. Mexico City, Mexico - 17,400,000
6. Osaka-Kobe-Kyoto, Japan - 16,425,000
7. Manila, Philippines - 14,750,000
8. Mumbai, India (formerly Bombay) - 14,350,000
9. Jakarta, Indonesia - 14,250,000
10. Lagos, Nigeria - 13,400,000
11. Kolkata, India (formerly Calcutta) - 12,700,000
12. Delhi, India - 12,300,000
13. Cairo, Egypt - 12,200,000
14. Los Angeles, United States - 11,789,000
15. Buenos Aires, Argentina - 11,200,000
16. Rio de Janeiro, Brazil - 10,800,000
17. Moscow, Russia - 10,500,000
18. Shanghai, China - 10,000,000
19. Karachi, Pakistan - 9,800,000
20. Paris, France - 9,645,000
21. Nagoya, Japan - 9,000,000 (tie)
21. Istanbul, Turkey - 9,000,000 (tie)
23. Beijing, China - 8,614,000
24. Chicago, United States - 8,308,000
25. London, United Kingdom - 8,278,000
26. Shenzhen, China - 8,000,000
Source: Demographia.
