The United States Code explicitly limits the total number of general officers (termed flag officers in the Navy and Coast Guard) that may be on active duty at any given time. The total number of active duty general officers is capped at 231 for the Army, 62 for the Marine Corps, 198 for the Air Force, and 162 for the Navy. 
A brigadier general ranks above a colonel and below a major general. The pay grade of brigadier general is O-7. It is equivalent to the rank of rear admiral (lower half) in the other United States uniformed services which use naval ranks. It is abbreviated as BG in the Army, BGen in the Marine Corps, and Brig Gen in the Air Force and Space Force.