Replicator rations were an energy-conservation policy instituted on the USS Voyager, limiting the usage of the ship's replicators for each crewmember. The use of rationing for the replicator was a policy that was not consistently implemented; rather, it was done when the ship's available power supplies were limited. When Voyager was able to replenish its energy reserves, rationing was discontinued. It was never clearly stated how this policy was implemented or enforced.
Because some objects needed more energy to replicate than others, a replicator ration was not simply equal to one use of the replicator. Instead, a replicator ration was equal to a certain amount of energy used by the replicator for producing the requested object. For example a clarinet, a complicated object to replicate, required a week's worth of rations as opposed to one ration to use the replicator one time. (VOY: "Parturition") Tom Paris' present for Kes, a locket, required two week's worth of rations. (VOY: "Twisted")
Shortly after the use of replicator rations was implemented on Voyager in 2371, Captain Janeway attempted to use one of hers to replicate some coffee, but was dissuaded by Neelix, who advised her to set an example for the crew by using restraint. (VOY: "The Cloud")
The next year, Lieutenant Paris started a gambling operation, wherein participants would attempt to guess the radiogenic particle count the following day at twelve hundred hours, using a pot of replicator rations. When Commander Chakotay found out about the game, he put a stop to it, stating that running a gambling ring was not appropriate behavior for a senior officer. (VOY: "Meld")
The year after that, after Paris and Harry Kim were released from the Akritirian maximum security detention facility, Paris suggested blowing a week's worth of replicator rations on the special meal they had fantasized about while in the prison. (VOY: "The Chute")
In 2376, Paris pleaded with Neelix for replicator rations so he could replicate a 2342 Mouton Rothschild champagne, a Terellian pheasant, and a rose to celebrate his two-year anniversary with B'Elanna Torres. (VOY: "Warhead")