Cuddalore is located at . It has an average elevation of . The land is completely flat with large deposits of black and alluvial soil inland and coarse sand near the seashore. The sandstone deposits in the town are popular. The Pennayar river runs north of the town, while Gadilam river runs across it. Cuddalore is situated at a distance of from the state capital Chennai and from Puducherry, the neighbouring union territory. The nearest airport is at Chennai, kilometres from Cuddalore. According to 2011 census, Cuddalore had a population of 173,636 with a sex-ratio of 1,026 females for every 1,000 males, much above the national average of 929. A total of 17,403 were under the age of six, constituting 8,869 males and 8,534 females. Scheduled Castes and Scheduled Tribes accounted for 13.22% and .3% of the population respectively. The average literacy of the city was 78.92%, compared to the national average of 72.99%.