Brundage is located at 28°35'42" North, 99°39'45" West (28.595243, -99.662611).
According to the United States Census Bureau, the city has a total area of 23.50 mi2 (60.87 km2). 23.40 mi2 (60.61 km2) of it is land and 0.10 mi2 (0.26 km2) of it is covered by water. The total area is 0.43% water.
Brundage is located in the Central Standard Time (CST) timezone, GMT-06:00. It observes Daylight Saving Time (DST).