Rear admiral ( United States ) The uniformed services of the United States are unique in having two grades of rear admiral s . Rear admiral ( lower half ) . In the United States Navy , the United States Coast Guard , the United States Public Health Service Commissioned Corps , the National Oceanic and Atmospheric Administration Commissioned Corps , rear admiral ( lower half ) ( RDML ) is a one - star flag officer , with the pay grade of O - 7 . Rear admiral ( lower half ) ranks above captain and below rear admiral . Rear admiral ( lower half ) is equivalent to the rank of brigadier general in the other uniformed services , and equivalent to the rank of commodore in most other navies . Rear admiral . In the United States Navy , the United States Coast Guard , the United States Public Health Service Commissioned Corps , the National Oceanic and Atmospheric Administration Commissioned Corps and the United States Maritime Service , rear admiral ( RADM ) , also referred to as rear admiral ( upper half ) , is a two - star flag officer , with the pay grade of O - 8 . Rear admiral ranks above rear admiral ( lower half ) and below vice admiral . Rear admiral is equivalent to the rank of major general in the other uniformed services . History . In 1981 , expanded commodore from a title to an official permanent grade by creating the one - star rank of commodore admiral . After only 11 months , the rank was reverted to just commodore but kept the one - star insignia . Then in 1985 , renamed commodore to the current grade of rear admiral ( lower half ) . Up until 1981 , all rear admirals wore two stars on their shoulder bars and rank insignia . Since then , rear admirals ( lower half ) wear one star while rear admirals ( upper half ) wear two ; verbal address remains " rear admiral " for both ranks . On correspondence , where the rear admiral ' s rank is spelled out , an ( LH ) and ( UH ) follows the rear admiral ' s rank title to distinguish between one and two stars . The Navy , Coast Guard , and NOAA Corps use the rank abbreviations RDML ( one - star ) and RADM ( two - stars ) , while the Public Health Service use the abbreviation RADM for both . The flags flown for rear admirals of the unrestricted line have one or two white , single - point - up stars on blue fields for the lower half or upper half , respectively . The flags of restricted line officers and staff corps officers have blue stars on a white field . and officially lists the two - star grade as rear admiral and not rear admiral ( upper half ) . However , the four uniformed services tend to list the rank as rear admiral ( upper half ) to help the general public distinguish between the two grades . United States Maritime Service . Although it exists largely as a maritime training organization , the United States Maritime Service does use the rank of rear admiral ( upper half ) and rear admiral ( lower half ) . By law , the Service has the same rank structure of the United States Coast Guard , but its uniforms are more similar to the United States Navy . Statutory limits . U . S . Code of law explicitly limits the total number of flag officers that may be on active duty at any given time . The total number of active duty flag officers is capped at 216 for the Navy . Some of these slots are reserved or set by statute . For example the Deputy Judge Advocate General of the Navy is a rear admiral ( upper half ) in the Navy . In the Coast Guard , the Chief Medical Officer is also rear admiral ( upper half ) . In the Public Health Service Commissioned Corps , at least half of the Assistant Surgeons General are rear admiral ( lower half ) and no more than half are rear admiral ( upper half ) . Officers serving in certain intelligence positions are not counted against the statutory limit . Promotion , appointment , and tour length . To be promoted to the permanent grade of rear admiral ( lower half ) or rear admiral , officers who are eligible for promotion to these ranks are screened by an in - service promotion board comprising other flag officers from their branch of service . This promotion board then generates a list of officers it recommends for promotion to flag rank . This list is then sent to the service secretary and the joint chiefs for review before it can be sent to the president , through the defense secretary for consideration . The president nominates officers to be promoted from this list with the advice of the Secretary of Defense , the service secretary , and if applicable , the service ' s chief of staff or commandant . The President may nominate any eligible officer who is not on the recommended list if it serves in the interest of the nation , but this is extremely rare . The Senate must then confirm the nominee by a majority vote before the officer can be promoted . Once confirmed , a nominee is promoted once he or she assumes an office that requires and / or allows an officer to hold that rank . For positions of office that are reserved by statute , the President nominates an officer for appointment to fill that position . For the Navy and the Coast Guard , because the one - star and two - star grades are permanent ranks , the nominee may still be screened by an in - service promotion board to add their input on the nominee before the nomination can be sent to the Senate for approval ; for the two commissioned corps , they normally go directly to the Senate . The standard tour length for most rear admiral positions is three years , but some are set at four or more years by statute . Since both grades of rear admiral are permanent , the ranks do not expire when the officer vacates a one - star or two - star position . Tradition . By tradition in the United States Navy , when an officer is selected or appointed to flag rank all current Navy flag officers write the selectee a letter congratulating him or her for attaining flag officer status . Retirement . Other than voluntary retirement , statute sets a number of mandates for retirement . All one - star officers must retire after five years in grade or 30 years of service , whichever is later , unless they are selected or appointed for promotion or reappointed to grade to serve longer . All two - star officers must retire after five years in grade or 35 years of service , whichever is later , unless selected or appointed for promotion or reappointed to grade to serve longer . Otherwise all flag officers must retire the month after their 64th birthday . However , the Secretary of Defense can defer a flag officer ' s retirement until the officer ' s 66th birthday and the President can defer it until the officer ' s 68th birthday . Flag officers typically retire well in advance of the statutory age and service limits , so as not to impede the upward career mobility of their juniors .