The choice of a particular architectural solution when designing a building considerably influences the costs of its construction. Generally speaking, the more complex the form of the horizontal projection is, the greater expenditures for the construction must be paid. The article presents the indexes which may relate to the complexity of the building shape, and which were then specified and compared on a particular example. For the chosen elements of the example building the change in expenditures were analyzed in relation to the degree of complexity of the shape. Examples of the influence of the building shape on the size of the usable floor area and costs of formwork of the premises were also discussed.