San Carlos is located at 26°17'43" North, 98°4'17" West (26.295278, -98.071389).
According to the United States Census Bureau, the city has a total area of 1.79 mi2 (4.65 km2). 1.79 mi2 (4.65 km2) of it is land and none of the area is covered by water.
San Carlos is located in the Central Standard Time (CST) timezone, GMT-06:00. It observes Daylight Saving Time (DST).