Calarasi County is located in the Romanian Plain, at the Danube, in the historical Muntenia province. It is bordered by the Giurgiu, Ilfov, Ialomita and Constanta counties. To the south, on the Danube, is the border with Bulgaria.
It has an area of 5088 sq km and a population of 316,294 inhabitants. Calarasi County has 2 municipalities, 3 cities and 48 communes. The county seat is Calarasi.