How city area is measured in Brazil

What "city" means in Brazil

The legal unit behind a Brazilian city name is the município. A município covers its whole territory, rural land included, not just the town it is named after. IBGE publishes an official territorial area for every município in its annual Áreas Territoriais files: the area of the legal territorial unit.

Above the município sits the região metropolitana (metropolitan region). It is created by state law. The Região Metropolitana de São Paulo has 39 municípios, according to the state transport agency EMTU.

IBGE also maps the physical city. Its Áreas Urbanizadas do Brasil survey traces built-up land by visual interpretation of satellite imagery, with 2019 as the reference year, and groups contiguous built-up municípios into concentrações urbanas (urban concentrations). The São Paulo urban concentration has 37 municípios, two fewer than the metropolitan region. IBGE splits its urbanized area into densely and sparsely built-up land, and lists empty subdivisions separately.

So a figure labelled "São Paulo" can describe a legal territory, a state-defined region or a measured footprint. These answer different questions: who governs the land, which municípios plan together, and where the buildings actually are.

Why our map may show a different number

When we have no stored boundary for a city, the app sends OpenStreetMap's Nominatim service a search for the city name and country, restricted to cities. On 17 October 2026, "São Paulo, Brazil" returned OpenStreetMap relation 298285, an administrative boundary of type municipality, displayed as "São Paulo, Região Sudeste, Brasil". That is the São Paulo município, not the metropolitan region or the built-up area. "Altamira, Brazil" returned relation 185554, also an administrative boundary, displayed as "Altamira, Pará, Região Norte, Brasil": the Altamira município. Both results are relations with their own polygons; the app draws a result like that directly and does not mark it approximate.

Measured by us from OpenStreetMap on 17 October 2026, both outlines come within one percent of the IBGE 2025 figures: the São Paulo outline measures slightly more than 1,523 km²^1,2, and the Altamira outline slightly more than 159,533 km²^5,6. The OpenStreetMap relations carry the same municipal codes IBGE uses. The two measurements still differ slightly, so an area calculated from these outlines will not exactly match the IBGE figure.

If you are looking for the size of Greater São Paulo, the outline these searches returned will understate it: the município is only one of the 39 municípios in the metropolitan region.

Problems getting boundaries in Brazil

The first problem is that the official number changes from edition to edition. IBGE publishes a new edition of every município's area each year, and São Paulo's figure in the 2025 edition differs from the one in earlier editions. A município area without its edition year is ambiguous, which is why every IBGE area on this page carries one. Changes can reach the national level too: IRIB, reporting an IBGE release, says Brazil's total area went down in IBGE's 2024 calculation because the international border was drawn more precisely.

The second problem is that official publishers give different numbers for the same place. The São Paulo city government states an area of its own, close to IBGE's 2025 figure but not equal to it, with no reference year on the page. The figures were published separately by different publishers, and neither source explains the difference. Even within one IBGE document, the urbanized-area report gives São Paulo one value in its text and a marginally different one in its ranking table; we publish the table value.

The third problem is the metropolitan region. OpenStreetMap maps the Região Metropolitana de São Paulo as an administrative boundary, but we do not publish an area for it here. The IBGE figure we found dates from the 2010 Census and does not state its unit alongside the value in a way we can quote directly, and the state transport agency's figure has no reference year and no independent second source. Until we can cite one properly, we leave the region undrawn.

Finally, we found no OpenStreetMap boundary for the urbanized area. It is a footprint traced from satellite imagery, not an administrative unit, so it cannot be drawn from OpenStreetMap the way a município can.