How big is Tokyo? There are at least three correct answers. The 23 special wards that most visitors think of as the city cover about 627 km². The Tokyo Metropolis, the prefecture-level government, covers 2,194 km². The Greater Tokyo Area, where roughly 37 million people live and commute, spans about 13,572 km².
Pick a different answer for each city and you can make almost any comparison come out the way you want. This primer covers the four things that most often skew a city size comparison: which boundary is being measured, how a dataset defines “city”, what population density adds, and how web maps distort size. It ends with a short checklist.
1. Three boundaries, three answers
Administrative area is the land a city government legally controls. It is the figure most city rankings use, and the one City Map Compare shows first on each city page. Metropolitan area adds the surrounding towns and suburbs tied to the city by commuting, as defined by a statistics agency. Built-up area traces the continuous urban footprint visible from above, regardless of borders.
The gap between the first two can be enormous. For the cities in our dataset with both figures, these have the largest ratio of metro area to city area:
| City | City area (km²) | Metro area (km²) | Metro ÷ city |
|---|---|---|---|
| Paris | 105 | 17,174 | 164× |
| Miami | 143 | 15,890 | 111× |
| Washington D.C. | 177 | 14,412 | 81× |
| Osaka | 225 | 13,228 | 59× |
| San Francisco | 121 | 6,984 | 58× |
| Boston | 232 | 11,700 | 50× |
Paris is the extreme case. Its city limits have barely moved since 1860, so the 105 km² City of Paris holds about 2.2 million people while the metropolitan area around it holds 12 million. Comparing the City of Paris with a city whose limits take in its suburbs measures two different things.
2. Check what the dataset calls a “city”
Even administrative areas are not defined the same way everywhere. Beijing (16,411 km²) and Shanghai (6,341 km²) are province-level municipalities whose borders include farmland, mountains and rural districts far from the urban core.
The Australian cities in our dataset use Greater Capital City areas, the official statistical regions that cover each metropolis. That is why Sydney appears as 12,368 km² and Brisbane as 15,826 km², even though the City of Sydney council itself governs only about 26 km² around the CBD. When a comparison looks wildly lopsided, check which definition each side uses before drawing conclusions.
3. Area without population tells half the story
A large area can mean a sprawling city or a boundary drawn around a lot of empty land. Population density helps tell the two apart. Manila packs about 43,023 people into each square kilometer of its 43 km² city proper. Brisbane's figure works out to 171, mostly because its boundary takes in forest, farmland and low-density suburbs.
Density has its own boundary problem, since it depends on the same area figure. Treat it as a rough signal, and compare cities measured the same way. Our guide to Houston and the European capitals shows how far apart two cities of similar area can be once population enters the picture.
4. Web maps make far-north and far-south cities look bigger
Nearly every online map uses the Web Mercator projection, and City Map Compare draws its tiles with it too. It keeps shapes recognizable but stretches distances as you move away from the equator, by a factor of 1 ÷ cos(latitude). Area is stretched by the square of that factor.
| City | Latitude | Distances drawn | Areas drawn |
|---|---|---|---|
| Singapore | 1.4° N | 1.00× | 1.00× |
| Mumbai | 19.1° N | 1.06× | 1.12× |
| Tokyo | 35.7° N | 1.23× | 1.52× |
| New York | 40.7° N | 1.32× | 1.74× |
| London | 51.5° N | 1.61× | 2.58× |
| Helsinki | 60.2° N | 2.01× | 4.04× |
Put two cities side by side at the same zoom level and the comparison is fair only when they sit at similar latitudes, such as Shanghai and Tokyo or London and Berlin. When they do not, the city closer to a pole is drawn too large. At one zoom level, London would appear 1.6 times wider and 2.6 times larger in area next to Singapore than it really is. Helsinki, at 60° north, is drawn about 4 times its true area compared with a city on the equator.
City Map Compare corrects for this. The second map is zoomed in or out by the ratio of the two latitude factors, so both maps share one ground scale and the scale bar is true for both. In London vs. Singapore the London map sits about 0.68 zoom levels further out than Singapore's. Other web maps and screenshots taken at matching zoom levels do not do this, so check the latitude before trusting a comparison you see elsewhere.
A checklist for honest city comparisons
- Compare the same kind of boundary on both sides: city with city, metro with metro.
- Check how the source defines each city, especially municipalities and statistical regions.
- Look at population and density next to area.
- On ordinary web maps, judge size by eye only for cities at similar latitudes.
- Use a tool that matches ground scale, or the area figures, for cities far apart north to south.
- Say which figure you used when you share a comparison.
Try it
- London vs. Paris — similar latitude, very different boundaries.
- Sydney vs. Melbourne — two Greater Capital City areas.
- Tokyo vs. New York
- Helsinki vs. Jakarta — one of the widest latitude gaps in our dataset, at one ground scale.
For rankings of all 97 cities, see world cities ranked by area, or open the comparison tool.