The largest city in the world by area depends on what you count as a city. By official boundaries, the largest is Hulunbuir in Inner Mongolia, a Chinese "prefecture-level city" of about 264,000 km², larger than the United Kingdom. Brazil's Altamira, at about 159,500 km², is the largest ordinary municipality, and Chongqing, at 82,403 km², is the largest Chinese municipality. By continuous built-up land, the largest urban area is New York's, at roughly 12,000 km² on the widest measure, followed by Tokyo–Yokohama at about 8,200 km².
Those answers are very different because the three rankings measure three different things. None of them is wrong. The trick is knowing which question each one answers.
Three Ways to Measure a City
The first measure is the administrative area: whatever the government has drawn as the city boundary. This is the least comparable, because countries draw those lines in completely different ways. A Chinese "city" can be the size of a province and include whole mountain ranges, while the City of London covers barely 3 km².
The second is the built-up urban area, the continuous spread of buildings, roads and paved land, wherever political boundaries fall. This is the one geographers prefer for comparisons, but it depends on the rules used to decide where the city stops, such as how big a gap of fields breaks it into separate places.
The third is the metropolitan area: the built-up core plus the towns and countryside connected to it by commuting. This is useful for economics and is always the largest of the three.
The Paper Giants: Largest by City Limits
| City | Official area | What the boundary contains |
|---|---|---|
| Hulunbuir, China | ~264,000 km² | Grassland, forest and about 2.2 million people |
| Altamira, Brazil | ~159,500 km² | Mostly Amazon rainforest; about 125,000 people |
| Chongqing, China | 82,403 km² | A province-level municipality of about 32 million |
| Hangzhou, China | ~16,850 km² | City, suburbs and hill country |
| Beijing, China | 16,410 km² | Includes mountains and part of the Great Wall |
| Kinshasa, DR Congo | 9,965 km² | A city-province, much of it rural |
| Sitka, USA | ~7,400 km² of land | Island and mainland Alaska; about 8,500 people |
China is behind most of these entries because of the way it defines cities. A prefecture-level city is really a region: an urban core surrounded by the counties it governs, which is how Hulunbuir comes to cover a large part of north-eastern Inner Mongolia. Chongqing, Beijing, Shanghai and Tianjin go one level higher. They are municipalities governed directly by the central government, with the same rank as provinces. Chongqing's 82,403 km² is about the size of Austria and contains dozens of separate towns, farmland and the Three Gorges stretch of the Yangtze.
Brazil's municipalities work the same way without the political rank. Every piece of Brazilian land belongs to some município, so in the thinly settled north a single municipality can take in a stretch of rainforest larger than most European countries. Alaska produces the American record for similar reasons: Sitka and Juneau are consolidated city-boroughs that include mountains, ice fields and fjords. For comparison, New York City covers about 780 km² of land, Greater London 1,572 km² and the Tokyo Metropolis 2,194 km², including its outlying islands.
Largest by Built-Up Area
Measured by continuous development, the ranking looks nothing like the one above. Demographia's World Urban Areas report, which applies one method to every city, puts the New York urban area at about 12,000 km². It stretches from central New Jersey across Long Island and into Connecticut. Tokyo–Yokohama comes second at about 8,200 km².
Even this ranking depends on its rules. The US Census Bureau uses its own definition and gave the New York–Newark urban area about 8,400 km² in 2020. The difference comes from how each method treats low-density suburbs and small gaps in development. Whichever figure you use, American metros take a disproportionate share of the top places, because low-density housing and car-based suburbs spread a given number of people over far more land. Atlanta is the standard example. It has fewer people than London but covers several times the area.
Tokyo–Yokohama shows the opposite pattern. It houses more than 35 million people, nearly twice New York's urban population, on two-thirds of the land, because rail rather than roads shaped its growth. We look at why cities grow outward in our guide to urban sprawl.
How Boundaries Grow
City limits are not fixed, and several of the best-known expansions were political decisions.
Moscow more than doubled overnight on 1 July 2012, when it annexed a wedge of Moscow Oblast running south-west towards Kaluga. Its area went from about 1,090 km² to about 2,560 km², although most of the new land was forest and villages. The plan was to move federal ministries into the new territory, known as New Moscow, but that part was quietly dropped.
Los Angeles covered about 73 km² when it was incorporated in 1850 and about 1,300 km² today. The biggest single step came in 1915, when the San Fernando Valley voted to join the city to get water from the new Los Angeles Aqueduct, a 375 km channel from the Owens Valley that had opened in 1913. Only the city was allowed to supply its water.
Jacksonville, Florida, merged with Duval County in 1968 and became the largest city by area in the contiguous United States, at about 2,265 km². Mergers like this, and China's reclassification of rural counties as urban districts, explain most of the eye-catching numbers in city-limits rankings. They record administrative changes, not growth.
Cities That Chose Not to Spread
Some of the world's largest cities are smaller on the ground than their populations would suggest because planners deliberately stopped them spreading. London's Metropolitan Green Belt, set up from the 1930s and formalised in the 1950s, rings the city with protected countryside. That is a large part of why Greater London's built-up area has hardly grown in seventy years while its population has returned to its 1939 peak and passed it. Seoul adopted a similar greenbelt in 1971. Portland, Oregon, has had an urban growth boundary since 1979, a legal line outside which most development is barred.
Physical limits do the same job elsewhere. Hong Kong has plenty of land but builds on only about a quarter of it, because most of the rest is steep country park. Its residents therefore live at very high densities along a narrow strip of flat coast and reclaimed land. Mexico City and Bogotá fill high basins ringed by mountains, and their newest informal neighbourhoods are climbing the slopes because there is nowhere flatter left to build.
Measuring Cities From Space
Because boundaries vary so much, researchers increasingly measure cities from satellite images instead of maps. The European Commission's Global Human Settlement Layer divides the whole planet into 1 km squares and classifies each by population and built-up cover. In 2020 the UN Statistical Commission endorsed a method built on it, the Degree of Urbanisation, as the standard for comparing cities between countries. Under that method a city is a continuous cluster of dense squares with at least 50,000 people, whatever local boundaries say. It produces rankings that often disagree with official figures, and it is the closest thing to a like-for-like comparison of city size that exists.
Area Is Not Density
A large footprint says little about how many people live on it. Manila's city proper packs about 43,000 people into each square kilometre, among the highest densities on Earth. Mumbai's Dharavi squeezes an estimated 600,000 to a million people into about 2 km², far denser than any city average. Manhattan manages about 28,000, and Paris inside its périphérique about 20,000 on 105 km². The city of Houston, with almost no zoning, averages about 1,400 across more than 1,600 km² of city limits. Our ranking of the most densely populated cities covers the other end of the scale.
Big Cities With Small City Limits
The opposite problem makes some major cities look far smaller than they are. The city of Paris has kept essentially the same boundary since 1860, when it annexed the villages inside its fortifications. It covers just 105 km², including two large parks, and holds about 2.1 million people. Most of the urban area of more than 10 million lives outside the city in separate communes. A metropolitan authority, the Métropole du Grand Paris, was created in 2016 over about 814 km² to coordinate planning, but it did not merge the communes. Manila's city proper is even smaller, at under 43 km², within a Metro Manila of sixteen separate cities and one municipality. Rankings by city limits therefore understate these cities as badly as they overstate Chongqing.
Which Answer to Use
For a quiz answer, give both: Hulunbuir (or Chongqing, if the question means municipalities) by official boundary, and New York by built-up area. To compare how big cities really are on the ground, use built-up area and name the source, because the definitions vary. Population rankings follow the same logic and have the same arguments about boundaries, as our explainer on what counts as a megacity shows.