A milling machine includes a cutting rotor, a foldable conveyor, a sensor, and a controller. The cutting rotor is configured to mill material beneath the milling machine. The foldable conveyor is configured to receive and dispose the milled material and includes a first section and a second section foldable with respect to the first section at a fold structure. The sensor is positioned on the milling machine and configured to sense a value indicative of a force acting on the second section. The controller is configured to determine an amount of the milled material within the second section of the foldable conveyor using the value indicative of the force.