There are varying definitions of the megalopolis, but it is generally seen as encompassing the administrative regions of Central Luzon, Calabarzon, and Metro Manila.

It is also being used more and more recently in planning for infrastructure projects by the government, particularly by the National Economic and Development Authority (NEDA) and the Japan International Cooperation Agency (JICA).

Meanwhile, the NEDA study, which is a collaboration with the Japan International Cooperation Agency (JICA), considers Metro Manila, Central Luzon, and Calabarzon as the Greater Capital Region (GCR).

[3] TV ratings agency AGB Nielsen Philippines and Kantar Media Philippines consider Metro Manila and the provinces of Bulacan, Cavite, Laguna and Rizal as "Mega Manila"[4] for their TV ratings gathering (area highlighted in blue on the map), a much stricter definition than the PIA.

Thus the academic definition as used for urban studies for built-up area surrounding Manila requires yet another term (e.g.

This means 38.6 percent of Philippine's total population all live inside Mega Manila.