A method for calculating a shape includes dividing an aspherical test surface into a plurality of measurement regions configured to overlap with one another, receiving, at a light receiving unit, interference fringes which occur due to interference light generated by light reflected on a reference surface serving as a reference for calculating a shape of the test surface and light reflected by each of the measurement regions, and calculating surface shapes of the measurement regions, and calculating a shape of the test surface by joining the calculated surface shapes, wherein the calculation of surface shapes includes adjusting relative positions of the test surface and the reference surface and adjusting a position of the light receiving unit so that the test surface and the light receiving unit have a conjugate relationship with each other in a state in which the position of the test surface is adjusted.