The following text is a reprint from an article that appeared in a Mid-80's magazine called CAPTAIN'S LOG.
OFFICER RANKS in the StarFleet Universe
Most gamers have at least a rudimentary idea of military ranks. For those who seek more understanding of ranks and their interrelationship, perhaps to refer to in playing out your own fictions, we offer this brief discussion.
The ranks in the Star Fleet Universe, and those used in film background, are based on those of the US and British Navy (and, to a lesser extent, Army). Most of the races in the Star Fleet Universe are presented as using these same ranks, which are listed below from lowest to highest.
COMMISSIONED OFFICERS
These are the officers of a starship and the most common types seen in fiction. Because of the nature of naval (and starship) combat, virtually all dialog is between officers.
CADET: A student at a military academy who has not yet been graduated and commissioned, but might be aboard a ship for a training cruise. Naval cadets are properly known as Midshipman because on old sailing ships they lived and ate in the middle of the ship, while the crew lived forward and the officers lived in the stern.
ENSIGN: The lowest of officer ranks; "working" officers on their first cruise. Because an officer is an officer, ensigns sometimes are assigned to command small units or to perform certain tasks. The rank insignia is one gold pip. This rank is equal to the Klingon rank of K1.
LIEUTENANT JUNIOR GRADE: The junior form of a lieutenant. A "working" officer, usually on his second or third cruise. Sometimes a deputy department head or possibly a PF skipper. The insignia is one gold pip and one blue pip. This rank is equal to the Klingon rank of K2.
LIEUTENANT: Perhaps the most common officer on board a ship. The "working" officers who actually push the buttons are lieutenants and ensigns, and full lieutenants are those with the most skill and seniority. A lieutenant might command a very small ship (perhaps an armed freighter or Klingon E3) or a fighter squadron. Lieutenants might be head of a minor department (administration). The insignia is two gold pips. This rank is equal to the Klingon rank of K3, or the Lyran rank of first claw.
LIEUTENANT COMMANDER: Might be the skipper of a frigate or police ship with the understanding that he will be promoted if he can handle the job. The insignia is two gold and one blue pip. This rank is equal to the Klingon rank K4, and the Lyran rank second claw, and the Romulan rank of Centurion.
COMMANDER: Usually a skipper for a smaller warship (frigate or destroyer). These officers are generally expected to be promoted upon completion of a successful tour to Captain. The insignia is three gold pips. This rank is equal to the Klingon rank K5, the Romulan Tribune, and the Lyran third claw.
CAPTAIN: The skipper of most "cruiser" class warships. It is the rank most people think of when thinking about commanding a ship. The insignia is four gold pips. This rank is equal to the Klingon rank K6, and the Romulan Sub-Commander, and the Lyran fourth claw.
FLEET CAPTAIN: This rank appears only in the Federation Star Fleet, and in fact only once in a film episode, where it was undefined. In the Star Fleet Universe, the title is bestowed on the senior Captain of a numbered fleet, such as the Sixth Fleet. The Admiral commanding the fleet may use this respected and experienced officer as a Squadron Commander or perhaps as an advisor, or instructor. No Klingon, Romulan, or Lyran equivalent.
FLAG OFFICERS
These are senior officers who never command a single ship.
COMMODORE: One star insignia. A flag officer but not an Admiral. Commander of a group of 4-6 ships know as a Squadron or Division. (Battle group in the UDF) Fleet Captains could command some units of this type. This rank is equal to the Klingon rank of Commodore K7, the Romulan Commander, and the Lyran First Fang.
REAR ADMIRAL: Two star insignia. Commander of an operational fleet of 11 ships. (Intruder insertion:Is a Battle Station Commander when the operational fleet is based there. ) This rank is equal to the Klingon rank of Wing Admiral K8, the Romulan Sub-Admiral, and the Lyran Second Fang.
VICE ADMIRAL: Three star insignia. Commander of a Sector. This rank is equal to the Klingon rank Group Admiral K9, the Romulan Senior Admiral, and the Lyran Third Fang.
FLEET ADMIRAL: Four star insignia. Commander of a numbered fleet or major command. This rank is equal to the Klingon rank Fleet Admiral K10, the Romulan Fleet Admiral, and the Lyran Fourth Fang.
GRAND ADMIRAL: Five star insignia. This rank is equal to the Klingon rank K11.
ADMIRAL-IN-CHIEF: The top military officer. Equal to the Klingon Grand Marshall K12, and the Romulan High Admiral.
This report is intended to entertain you and maybe explain some unasked questions. My hope is that you have enjoyed it.