More than half the world's people live in towns and cities, and some cities hold more people than whole countries. Which city is the biggest? The answer depends on where you draw a city's edge. You will need Crowded Places to see why.
Key idea
In the UN's 2025 count (World Urbanization Prospects), the largest cities are Jakarta, Indonesia (nearly 42 million people), Dhaka, Bangladesh (almost 40 million), and Tokyo, Japan (about 33 million). Nine of the top ten are in Asia; Cairo is the only one outside it. A megacity has 10 million people or more; there were 33 in 2025.
Why it works
A city has no sharp edge: suburbs and towns run into one another. One list counts only the city's official limits; another counts the whole built-up area; another counts everyone who commutes in. The UN's 2025 report uses a new method that counts the area where people actually live close together, using maps of population density. Its older 2018 list, using countries' own city boundaries, put Tokyo first, with about 37 million.
Worked example: Comparing two cities
In the UN's 2025 count, about how many more people does Jakarta have than Tokyo?
- Jakarta: nearly 42 million. Tokyo: about 33 million.
- 42 − 33 = 9.
Answer: About 9 million more.
Worked example: Why lists disagree
A book from 2019 says Tokyo is the largest city. Is the book wrong?
- It probably used the UN's 2018 list, which put Tokyo first.
- The 2025 report measures cities differently.
Answer: Not wrong for its source and year; lists differ in how they draw city edges.
Common mistake
People expect one fixed ranking of cities. In the UN's older lists Tokyo was first; the 2025 report, which measures cities by where people actually live close together, puts Jakarta first. When you quote a ranking, give its source and year.