A safety device for measuring and indicating the level of a ladder having rungs extending between a pair of elongated ladder rails, the safety device comprising a housing dimensioned to be inserted into one of the rungs of the ladder, an electronic sensor disposed in the housing, a controller disposed in the housing, which is in electronical communication with the sensor, at least one indicator, and a power supply for supplying power to the device. The electronic sensor measures the inclination of the ladder to produce a measured inclination which the controller compares to a stored predetermined level value to produce a comparison signal. The at least one indicator receives the comparison signal and indicates to the user the comparison signal.