Kolkata is located in eastern India at 22°33'N, 88°20'E in the Ganges Delta at an elevation ranging between 1.5 to 9 metres. It is spread linearly along the banks of the River Hooghly in a north-south direction. Much of the city was originally a vast wetland, reclaimed over the decades to accommodate the city's burgeoning population. The remaining wetland, known as East Calcutta Wetlands has been designated a "wetland of international importance" under the Ramsar Convention. Like most Indo-Gangetic plains, the main type of soil is wet. Quaternary sediments consisting of clay, silt, different grades of sand and gravel underlying the city. These sediments are sandwiched between two beds of clay, the bottom at depths between 250 and 650 m and higher ranging between 10 and 40 metres thick. According to the Bureau of Indian Standards, the city falls under seismic zone-III, in a scale of I to V (in order of increasing vulnerability to earthquakes), while wind and hurricane zoning is "very high risk damage, "according to the UNDP report.

Kolkata buildings in the city centre, under the jurisdiction of the Kolkata Municipal Corporation(KMC), has an area of 185 square kilometres (71 square miles). The Kolkata urban area, however, has continued to grow and, from 2006, the urban Agglomeration (Kolkata Metropolitan Area) spread over 1750 square kilometres (676 sq mi), and consists of 157 positions. The city is officially administered by several local governments including 38 local municipalities. The urban area is composed of 72 cities and 527 towns and villages. The suburban areas of Kolkata metropolitan district includes parts of the districts North 24 Parganas, South 24 Parganas, Howrah, Hooghly and Nadia.

The east-west dimension of the city proper is narrow, extending from the Hooghly River to the west, roughly the Eastern Metropolitan Bypass to the east, an area of just 5-6 km. Extending north-south is roughly divided into a northern, central and southern Kolkata. North Kolkata city is the oldest part of the city, with the architecture of the 19th century and narrow streets. South Kolkata grew mostly after independence and is composed of well-to-do communities. The Salt Lake City (Bidhan Nagar) to the north-east area of the city: a draft of the section of Kolkata. Rajarhat, also called the New Town, the township is planned under development on the north-eastern fringe of the city. Kolkata Central houses the central business district around the area of BBD Bagh. The Secretariat of Government, General Post Office, High Court, Lalbazar police headquarters and several other public and private organizations are located here. The Maidan is a large open field in the heart of the city, where several sports events and public meetings are held. Several companies have set up their offices in the area south of Park Street, which has become a central business district secondary.