There is described a grain level sensor system for a grain bin. The grain level sensor system has a floater which is arranged to sit on top of the level of grain in the grain bin. The floater is coupled with the outlet of a grain conveyor such that the height of the grain level in the bin can be calculated based at least in part by measuring the height of the floater above the conveyor outlet. Accordingly, the peak height of grain in the grain bin can be determined.