Provided are an electronic system, an image system, and a method for measuring particulate matter. The electronic system includes an illuminator, a sensor and a processor. The illuminator outputs light. The sensor includes a pixel array to generate an analog signal based on scattered light according to the output light, and a converting circuit to convert the analog signal into digital signals respectively corresponding to gain values, based on the gain values. The processor counts the number of values greater than or equal to a threshold value among values of the digital signals, and calculates a concentration of particulate matter having a target size range, based on a variation in the counted number according to a change of the gain values.