In the United States armed forces, a base commander is generally at least an O-6 grade officer, which means colonel (Army, Air Force, Marines) or captain (Navy, Coast Guard).
The post commander for most active duty installations is an O-7 grade officer (brigadier general) or higher, depending in the echelon housed.
For example, Wheeler Army Airfield on Oahu, Hawaii, houses the 25th Combat Aviation Brigade and is commanded by an O-6 (colonel).
Fort Cavazos houses three divisions and III Corps and is commanded by an O-9 (lieutenant general).
In the US Navy, the US Marine Corps and US Coast Guard, the commanding officer of a base, station, air station, support activity or other facility in an independent commander, typically supporting one or more tenant units.