Toner level sensing using rotatable magnets having varying angular offset

An electrophotographic image forming device according to one example embodiment includes a replaceable unit having a reservoir for storing toner and a rotatable shaft positioned within the reservoir. The replaceable unit has a first magnet and a second magnet connected to the shaft and rotatable around an axis of rotation of the shaft in response to rotation of the shaft. An amount of angular offset between the first magnet and the second magnet varies depending on an amount of toner in the reservoir. A sensor is positioned to sense the first magnet and the second magnet at a point in their rotational paths. A processor is in electronic communication with the sensor and configured to determine an angular offset between the first magnet and the second magnet and to adjust an estimate of the amount of toner remaining in the reservoir based on the determined angular.