You’d think counting people would be easy. It's basically just a head count, right? Honestly, though, when you start looking at the biggest cities by population, things get weirdly complicated. You’ve got one set of numbers for the "city proper," another for the "metropolitan area," and then the "urban agglomeration" crowd rolls in with their own data.
It's a mess.
If you ask a tourist, they’ll tell you Tokyo is the king. Ask a statistician at the UN in 2026, and they might point you toward Jakarta or Dhaka instead. The truth is that the title of "world’s largest city" depends entirely on where you draw the line in the dirt.
Why Jakarta is suddenly winning the biggest cities by population race
For decades, Tokyo was the undisputed heavyweight champion. It was the gold standard of megacities. But the latest 2025 and 2026 data from the UN World Urbanization Prospects has flipped the script. Thanks to a new way of measuring called the "Degree of Urbanization," Jakarta, Indonesia, has officially claimed the top spot.
We are talking about 41.9 million people.
That’s more than the entire population of Canada squeezed into one Indonesian urban sprawl. It’s hard to even wrap your head around that kind of density. Imagine every single person in a mid-sized country trying to use the same set of highways and train lines. That’s Jakarta.
The shift from Japan to South Asia
Tokyo is actually shrinking. Well, "shrinking" is a relative term when you still have 33.4 million people, but the trend is downward. Japan’s aging population is a real thing, and it’s showing up in the city stats. Meanwhile, cities like Dhaka in Bangladesh are exploding.
Dhaka is currently sitting at number two with about 36.6 million residents. If you've ever seen videos of the traffic there, you know it’s a city that’s literally bursting at the seams. Experts predict that by 2050, Dhaka will probably take the number one spot from Jakarta.
The big North American divide: Mexico City vs. The Rest
When we talk about the biggest cities by population in North America, Americans usually default to New York City. And yeah, NYC is huge. It has about 19.3 million people in its metro area as of 2026.
But Mexico City is the real giant of the continent.
It’s sitting at roughly 22.7 million people. It’s the only city in the Western Hemisphere that consistently competes with the Asian megacities. While New York has actually been losing a bit of its population—about 128,000 people since 2020—Mexico City just keeps humming along.
Interestingly, Los Angeles is the outlier in the US. While NYC, Chicago, and Philadelphia have seen slight dips, LA actually grew by nearly a quarter-million people over the last few years, hitting the 12.7 million mark.
What most people get wrong about city size
The biggest mistake people make is comparing "city limits" to "metro areas."
Take Miami, for example. If you just look at the city proper, it looks tiny—smaller than Fresno, California. But the Miami metro area has over 6 million people. This is why lists of the biggest cities by population are so frustrating to read. One list will put Chongqing, China, at the top because its administrative "city" is the size of Austria, while another list will leave it out because most of that land is actually rural farmland.
To get a real sense of size, you have to look at the "urban agglomeration." This ignores political borders and just counts the continuous "built-up" area.
The rising stars in Africa
If you want to know where the next big shift is happening, look at Africa. Cairo is currently the only non-Asian city in the global top ten, with 25.6 million people. It’s massive. But it’s not alone.
- Lagos, Nigeria: 12.8 million and growing fast.
- Kinshasa, DR Congo: 10.9 million.
- Luanda, Angola: 11.3 million.
These cities are transforming so quickly that the infrastructure can barely keep up. By 2050, cities like Dar es Salaam and Addis Ababa are expected to join the 10-million-plus "megacity" club.
The daily reality of living in a megacity
It’s not all about the numbers. Living in one of the biggest cities by population changes how you experience life. In Tokyo, it means "pushers" at train stations helping you fit into a subway car. In Dhaka, it means a commute that might take three hours to go ten miles.
There’s also a massive economic divide. You have the "Silicon Valley of Mexico" in Guadalajara (4.1 million) seeing high-tech growth, while other megacities struggle with basic sanitation for millions of people in informal settlements.
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How to use this data for your next trip
If you're planning to visit one of these giants, don't just look at the population count. Look at the density. A city like Manila is incredibly dense, which makes it feel much "bigger" and more chaotic than a spread-out city like Los Angeles.
Next steps for the curious traveler or researcher:
- Check the "Urban Agglomeration" stats instead of "City Proper" to avoid being misled by political boundaries.
- Use tools like Google Earth to see the actual physical footprint of these cities; it’s the only way to realize how big Jakarta actually is.
- Research the "commuter belt" if you're planning to stay in a megacity, as staying 10 miles out could mean a 2-hour journey.
The world is urbanizing at a breakneck pace. Whether we're ready for 50-million-person cities or not, they're coming.