Dryer appliances and methods for operating dryer appliances are provided. A method includes calculating an initial cycle time, and counting down from the initial cycle time for an initial countdown time. The method further includes determining, during the step of counting down from the initial cycle time for the initial countdown time, whether a load size value and an air flow value have been established. The method further includes calculating, when the load size value and the air flow value have been established, a first updated remaining cycle time based on the load size value and the air flow value.