As of 2008, the ward has an estimated population of 442,271 and a population density of 11,070 persons per km². The total area is 39.48 km².
Kōtō is located east of the Tokyo metropolitan center, bounded by the Sumida-gawa to the west and the Arakawa River to the east. Its major districts include Kameido, Kiba, Kiyosumi, Monzen-nakachō, Shirakawa, and Toyosu. The newly developed waterfront area of Ariake is in Kōtō, as is part of Odaiba.
Kōtō occupies a position on the waterfront of Tokyo Bay sandwiched between the wards of Chūō and Edogawa. Its inland boundary is with Sumida. Much of the land is reclaimed, so there are few old temples or shrines.
Noteworthy places in Kōtō include:
In the former ward of Fukagawa: Kiba, Fukagawa, Edagawa
In the former ward of Jōtō: Kameido, Ōjima, Sunamachi
On recently reclaimed land: Ariake, Yumenoshima, Tokyo Rinkai Fukutoshin