How city area is measured in Australia

What "city" means in Australia

Australia has no single legal definition of a city. Three kinds of area are used, and each gives a very different number.

The first is the local government area (LGA): the territory of one council. The City of Sydney and the City of Brisbane are both LGAs, and the Australian Bureau of Statistics (ABS) publishes their boundaries in its Australian Statistical Geography Standard (ASGS). The two councils cover very different shares of their cities. By our calculation from the ABS figures on this page, the City of Sydney is less than one percent of the Sydney urban area, while the City of Brisbane is about a fifth of the Brisbane urban area.

The second is the Significant Urban Area (SUA). The ABS defines SUAs as Urban Centres, or groups of Urban Centres, with a population of 10,000 or more.

The third is the Greater Capital City Statistical Area (GCCSA). The ABS builds GCCSAs from Statistical Areas Level 4 and says they represent the labour market and functional area of each capital city. They take in people who work or shop in the city but live in the small towns and rural areas around it, and the ABS itself warns that GCCSA boundaries may differ from official or commonly used boundaries. In ASGS Edition 3 the ABS defines 16 GCCSA regions, 8 of them for capital cities.

All the ABS figures on this page are boundary areas from the ABS 2021 boundary layers, published in a field the ABS names AREA_ALBERS_SQKM. This field gives one area per boundary, not separate land and water figures.

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, "Sydney, Australia" returned OpenStreetMap relation 5750005, a place boundary displayed as "Sydney, New South Wales, Australia". It is not a council boundary: OpenStreetMap tags it as a place, not an administrative area, and its note says it is based on the ABS Significant Urban Area for Sydney. "Brisbane, Australia" returned relation 14027280, also a place boundary rather than a council boundary, displayed as "Brisbane, Queensland, Australia", with the alternative name Greater Brisbane. Both results are relations with their own polygons; the app draws a result like that directly and does not mark it approximate.

So the outlines these searches returned are neither the City of Sydney council area nor the GCCSA. For Sydney, the search returned a shape based on the urban area. Measured by us from OpenStreetMap on 17 October 2026, that shape is about a seventh larger than the ABS figure for the Sydney Significant Urban Area, 4,197 km²^3,4; OpenStreetMap does not say which edition of the ABS boundary it follows. For Brisbane, our measurement of the shape is within one percent of the ABS figure for the Brisbane Significant Urban Area, 6,462 km²^9,10, though the relation does not say what it is based on. Either way, the outlines returned on that date are closer in area to the urban-area figures than to the council areas or the GCCSA.

Problems getting boundaries in Australia

The first problem is that a GCCSA is a statistical region, not a city. Greater Sydney, at 12,369 km²^5,6, is about three times the Sydney urban area by our calculation, and the ABS says GCCSAs include the small towns and rural areas around a city.

The second problem is that publishers disagree on the same council area. The ABS boundary layer gives the City of Sydney 26.7 km²^1,2, and the NSW Office of Local Government lists the same value at one decimal place. The City of Sydney itself says its area covers approximately 26.2 km²^11,12. The figures were published separately by different publishers, and neither source explains the difference. For Brisbane, the council's annual report gives a land area that matches the ABS boundary area at one decimal place.

The third problem is that we found no OpenStreetMap boundary for the GCCSAs. The council areas are mapped as administrative boundaries, and Sydney and Brisbane also appear as place boundaries. Greater Sydney and Greater Brisbane would have to be drawn from ABS boundary files, so we do not draw them here. We also do not publish an area for Greater Brisbane: the only second source we found does not cite a primary source.