A level sensor, associated with a bin, detects a particular reference level of an agricultural product in the bin and generates a calibration indicator. An input sensor determines an input rate of the agricultural product into the bin. A conveyer is capable of transporting the agricultural product out of the bin. An output sensor provides a status indicator that indicates whether the conveyer is in an active state or in an inactive state during one or more evaluation time windows. A data processor determines an output rate of the agricultural product based on the status indicator. The data processor comprises a level estimator for estimating an estimated bin level of the bin based on the input rate and an output rate. The data processor comprises a calibrator for calibrating the estimated bin level with reference to the particular reference level in response to the calibration indicator.