Big, Bigger, Gigantic: Megacities of the World !

Introduction

Have you ever wondered how many people live in cities around the world? Well, the United Nations (UN) says that as of 2025, nearly half of the people on Earth — about 45% — live in cities! That’s a huge number when you think that, in 1950, only 1 out of 5 people lived in cities. In this blog post, we’re going to take a look at the world’s biggest cities, where they are, which ones are super big, and how they’re changing.

What Counts as a ‘City’ ?

• The UN uses a special definition of “city” for this report: not just city limits or administrative borders, but urban areas that are dense and continuous — places where buildings are tightly packed, and there are at least 1,500 people per km².
• Also, for a place to count as a “city” in this system, it needs at least 50,000 people.
• This definition helps compare real urban places all around the world, even when countries count their cities differently.

How Many Cities Are There — and How Big?

According to the UN, there are over 12,000 cities (as of 2025) in this sense. Out of these, 33 are “megacities” — that means each of them has more than 10 million people! These megacities are mostly in Asia: 19 of the 33 are on that continent. Even though megacities are super famous, lots of people also live in small and medium-sized cities, and many of those are growing faster than the really big ones.

This map shows where these cities are. The legend tells us that the purple ones are the biggest !

Top 10 Biggest Cities (2025) — Meet the Giants !

Here are the top 10 biggest cities in 2025, according to the UN’s methodology.

These are huge numbers!

For example, Jakarta has more than double the population of many whole countries.

But let’s also look at how this Top 10 has changed from the year 2005 to now, and how we expect it to change from now until 2050. The following is called a “bump chart” and is often used to compare rankings over time. Notice how Tokyo, Japan is dropping in rank while Dhaka, Bangladesh and Karachi, Pakistan are growing very fast !

Why Are These Cities Growing So Much?

There are a few big reasons:

Urban Migration: Many people from rural areas are moving into cities for jobs, schools, and better services.

Birth Rate + Demographics: In some regions, cities are growing fast because of higher birth rates; in others, they grow as young people move in.

Urban Planning and Expansion: Cities are expanding outwards — more land is being turned into dense urban areas.

Regional Concentration: Asia (especially South and Southeast Asia) has a lot of population, so many of the fastest-growing megacities are there.

What Does This Mean for the Future?

The UN projects that by 2050, two-thirds of the world’s growth in population will happen in cities. That means city planning, housing, transport, and green spaces will be really important. For younger readers like you: more city life means more chances to build smart, sustainable cities — with clean energy, public transport, and green spaces. The report also hints that not all cities will grow forever: as urban systems mature, growth rates of very large cities may slow down, giving more growth to smaller cities.

Big Ideas & Take-Home Messages for Kids

• Cities are super important in our world: they are home to nearly half of all people.
• Megacities are amazing, but small and medium cities are growing fast, too — they’re not just “boring small towns.”
• Urban planning matters more than ever: how we design future cities can shape the lives of billions.
• You can make a difference: by learning about cities, you can think about what makes a “good city” — green parks, good transport, enough homes, and clean air.

Suggested Activities for Maps4Kids Readers

Here are a few fun, interactive ideas you could include at the end of the blog post to make it more engaging:

1. Map Quiz: Show a world map with empty spots — ask kids to guess which countries host the top 10 megacities.
2. City Comparison: Have kids pick two of the top 10 cities, then research what makes those cities special: their landmarks, climate, history.
3. Design Your Dream City: Ask kids to draw a city with 40 million people (like Jakarta) — where would they put green spaces, homes, schools, transport? For this, you can try a games like Sim City.