The archipelago is about 500 kilometres (310 mi) south of the Maldives, 1,880 kilometres (1,170 mi) east of the Seychelles, 1,680 kilometres (1,040 mi) north-east of Rodrigues island, 2,700 kilometres (1,700 mi) west of the Cocos (Keeling) Islands, and 3,400 kilometres (2,100 mi) north of Amsterdam Island.

The land area of the islands is 56.13 km² (21.7 sq.
miles), the largest island, Diego Garcia, having an area of 32.5 km².
The total area, including lagoons within atolls, is more than 15 000 km², of which 12 642 km² are accounted by the Great Chagos Bank, the largest acknowledged atoll structure of the world (the completely submerged Saya de Malha Bank is larger, but its status as an atoll is uncertain).
The shelf area is 20 607 km², and the Exclusive Economic Zone, which borders the corresponding zone of the Maldive Islands in the north, has an area of 639 611 km² (including territorial waters).

The Chagos group is a combination of different coralline rock structures topping a submarine ridge running southwards across the centre of the Indian Ocean, formed by volcanoes above the Réunion hotspot.
Unlike the Maldives, there is no clearly discernible pattern in the atoll arrangement, which makes the whole archipelago look somewhat chaotic.
Most of the coralline structures of the Chagos are submerged reefs.

The Chagos contain the world's largest coral atoll, The Great Chagos Bank, which supports half the total area of good quality reefs in the Indian Ocean.
As a result, the ecosystems of the Chagos have so far proven resilient to climate change and environmental disruptions.

The largest individual islands are Diego Garcia (32.5 km²), Eagle (Great Chagos Bank, 3.1 km²), Île Pierre (Peros Banhos, 1.40 km²), Eastern Egmont (Egmont Islands, 2.17 km²), Île du Coin (Peros Banhos, 1.32 km²) and Île Boddam (Salomon Islands, 1.27 km²).

In addition to the seven atolls with dry land reaching at least the high-water mark, there are nine reefs and banks, most of which can be considered permanently submerged atoll structures.
The number of atolls in the Chagos Archipelago is given as four or five in most sources, plus two island groups and two single islands, mainly because it is not recognised that the Great Chagos Bank is a huge atoll structure (including those two island groups and two single islands), and because Blenheim Reef, which has islets or cays above or just reaching the high-water mark, is not included.
Features are listed in the table from north to south:
The archipelago is about 500 kilometres (310 mi) south of the Maldives, 1,880 kilometres (1,170 mi) east of the Seychelles, 1,680 kilometres (1,040 mi) north-east of Rodrigues island, 2,700 kilometres (1,700 mi) west of the Cocos (Keeling) Islands, and 3,400 kilometres (2,100 mi) north of Amsterdam Island.
The land area of the islands is 56.13 km² (21.7 sq. miles), the largest island, Diego Garcia, having an area of 32.5 km². The total area, including lagoons within atolls, is more than 15 000 km², of which 12 642 km² are accounted by the Great Chagos Bank, the largest acknowledged atoll structure of the world (the completely submerged Saya de Malha Bank is larger, but its status as an atoll is uncertain). The shelf area is 20 607 km², and the Exclusive Economic Zone, which borders the corresponding zone of the Maldive Islands in the north, has an area of 639 611 km² (including territorial waters).
The Chagos group is a combination of different coralline rock structures topping a submarine ridge running southwards across the centre of the Indian Ocean, formed by volcanoes above the Réunion hotspot. Unlike the Maldives, there is no clearly discernible pattern in the atoll arrangement, which makes the whole archipelago look somewhat chaotic. Most of the coralline structures of the Chagos are submerged reefs.
The Chagos contain the world's largest coral atoll, The Great Chagos Bank, which supports half the total area of good quality reefs in the Indian Ocean. As a result, the ecosystems of the Chagos have so far proven resilient to climate change and environmental disruptions.
The largest individual islands are Diego Garcia (32.5 km²), Eagle (Great Chagos Bank, 3.1 km²), Île Pierre (Peros Banhos, 1.40 km²), Eastern Egmont (Egmont Islands, 2.17 km²), Île du Coin (Peros Banhos, 1.32 km²) and Île Boddam (Salomon Islands, 1.27 km²).
In addition to the seven atolls with dry land reaching at least the high-water mark, there are nine reefs and banks, most of which can be considered permanently submerged atoll structures. The number of atolls in the Chagos Archipelago is given as four or five in most sources, plus two island groups and two single islands, mainly because it is not recognised that the Great Chagos Bank is a huge atoll structure (including those two island groups and two single islands), and because Blenheim Reef, which has islets or cays above or just reaching the high-water mark, is not included. Features are listed in the table from north to south:
Chagos Archipelago