A combine having a feeder housing for receiving harvested crop, a separating system for threshing the harvested crop to separate grain from residue, a grain tank for storing the separated grain, a grain tank level sensor for detecting a level of grain in the grain tank, and a controller that controls the combine. The controller is configured to receive the level of grain from the grain tank level sensors, determine a volume of a grain base from the level of the grain, determine a volume of a grain heap above the grain base, determine a total volume by combining the volume of the grain base with the volume of the grain heap.
