1. An estimating apparatus comprising: specifying circuitry configured to specify a region of a subject irradiated with X-rays emitted from an X-ray tube of an X-ray CT apparatus on a human body model schematically representing the subject; deriving circuitry configured to assume the human body model to be at a position where the subject is arranged in radiography performed by the X-ray CT apparatus and derive an exposure dose of the X-rays on a surface of the region specified by the specifying circuitry on the human body model based on irradiation conditions in the radiography; and display control circuitry configured to display, on a display, information in which the exposure dose derived by the deriving circuitry is associated with the region on the human body model specified by the specifying circuitry.