An object amount calculation apparatus includes: a receiver configured to obtain a first three-dimensional model and a second three-dimensional model different from the first three-dimensional model, each of the first three-dimensional model and the second three-dimensional model representing a same space, each of the first three-dimensional model and the second three-dimensional model being constituted with regions having respective attributes; and a processor configured to: align the first three-dimensional model and the second three-dimensional model based on at least one attribute of the first three-dimensional model and the second three-dimensional model; calculate, for each of the attributes, a difference between the first three-dimensional model aligned and the second three-dimensional model aligned; and output (i) a total amount of differences corresponding to two or more attributes among the attributes and (ii) information on the two or more attributes.