A device and method for determining a roadway gradient quantity, which describes the gradient of a roadway on which a vehicle is situated, is described. The device includes a liquid container, which is mounted to the vehicle and contains a liquid, at least one pressure sensor, which is mounted in the bottom of the liquid container and is used to ascertain a pressure quantity which describes the hydrostatic pressure in the liquid container, and an evaluation unit to which the pressure sensor is connected. In the evaluation unit, the roadway gradient quantity is determined as a function of the pressure quantity.