The regency, which was established on 7 November 1956, covers an area of 2,127.25 square kilometres (821.34 sq mi) and according to the 2010 census it had a population of 350,479,[2] increasing to 404,998 at the 2020 Census;[3] the official estimate as at mid-2023 was 420,799, comprising 208,600 males and 212,200 females.

The GDP per capita of Karo Regency in 2005 was 11.65 million rupiah, approximately US$1,200.

[1] The table also includes the locations of the district administrative centres, the number of administrative villages in each district (totaling 259 rural desa and 10 urban kelurahan), and its post codes.

(c) comprising 4 kelurahan (Gundaling I, Gundaling Ii, Tambak Lau Mulgap I and Tambak Lau Mulgap Ii) and 6 desa.

Note that four of these districts (indicated by "*" above) constitute a part of the Medan metropolitan area.