How city area is measured in India

What "city" means in India

In both Mumbai and Delhi, the city name can refer to several different bodies, each with its own area.

Mumbai shows the layers. The Brihanmumbai Municipal Corporation governs Greater Mumbai, which had a population of 12,442,373 at the 2011 Census, according to the corporation's Year Book 2025. The corporation's own 2011 city profile describes the area under its administration as smaller than "Mumbai, as an urban entity", which also takes in Defence lands, Mumbai Port Trust lands and the Borivali National Park area. Beyond that is the Mumbai Metropolitan Region, a planning region defined by the Mumbai Metropolitan Region Development Authority (MMRDA). The MMRDA says it consists of 9 municipal corporations, 9 municipal councils and more than 1,000 villages in Thane, Raigad and Palghar districts. Greater Mumbai is only one of those corporations, and the region's 6,328 km²^9,10 is more than ten times either figure for the corporation.

Delhi is the National Capital Territory (NCT). The National Capital Region Planning Board lists the whole NCT as Delhi's part of the wider National Capital Region. Inside the NCT, the Municipal Corporation of Delhi (MCD) is the civic body for most of the territory, but not all of it. The New Delhi Municipal Council's page on the New Delhi Municipal Council Act, 1994 names three local bodies, each with its own area: the MCD, the New Delhi Municipal Council and the Delhi Cantonment Board. By our calculation, the three areas that page lists add up exactly to the NCT figure, 1,483 km²^5,6. The MCD itself has been reorganised: according to its own portal, three corporations (East, North and South Delhi) were re-unified into a single MCD on 22 May 2022, and it is now divided into 12 zones.

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, "Mumbai, India" returned a single point (OpenStreetMap node 16173235), displayed as "Mumbai, Mumbai Suburban District, Maharashtra, 400051, India", not a boundary. If the result is a point, the app looks for an enclosing administrative area named in the address (a municipality, city, town, village or county) and draws that instead, marked approximate. For Mumbai the only such name is "Mumbai" itself, and searching for it again returned only the same point. Nominatim therefore gives the app no polygon for Mumbai at all, approximate or otherwise.

The same search for "Delhi, India" returned OpenStreetMap relation 21180767, displayed as "Delhi, Old Delhi, Delhi, India". It is an administrative boundary at level 8, which OpenStreetMap tags with the operator "Municipal Corporation of Delhi". When no boundary is stored, the app draws a relation with its own polygon like this one directly and does not mark it approximate. The area we measured from that polygon on 17 October 2026 is within half a percent of the MCD's 1,397 km²^7,8, and smaller than the NCT's 1,483 km²^5,6. We have found no source that confirms the polygon's extent, so we do not present it as the MCD boundary. So the outline a Delhi search returns is smaller than the whole territory.

Problems getting boundaries in India

The first problem is that we found no OpenStreetMap relation confirmed as the boundary of either corporation on this page. Wikidata gives no OpenStreetMap relation for the Brihanmumbai Municipal Corporation or for the MCD, and the OpenStreetMap relation linked from Mumbai's Wikidata entry is a route, not a boundary. The corporation figures on this page are therefore shown in the tables but not drawn.

The second problem is that the boundaries OpenStreetMap does have do not always match the official figures. Its relation for the NCT is within one percent of 1,483 km²^5,6, so we draw it. Its relation for the Mumbai Metropolitan Region is not: when we fetched it on 17 October 2026, the area we measured from it was about two-thirds of MMRDA's 6,328 km²^9,10. We found no source that explains the gap, so we do not draw it.

The third problem is dates. Most figures on this page carry no reference date. The MCD figure appears on the corporation's current portal, and the New Delhi Municipal Council's page on its 1994 Act gives the same number; neither says whether it describes the corporation before or after the 2022 re-unification. MMRDA's figure for its region is undated too. The Mumbai figures come from documents published years apart, and neither says when its figure was measured.