An electronic device having a display and a sensor and methods for operating the same are provided. The electronic device includes a housing, a display disposed on a surface of the housing, a sensor mounted under the display inside the housing to detect light received through the display, and a processor electrically connected with the display and the sensor, wherein the processor is configured to determine an illuminance of an outside of the housing using detection data obtained by the sensor while the display displays an image and relevant information between the display and the sensor.