This standard defines a method for the sizing of nonfunctional software requirements. It complements ISO/IEC 20926:2009 which defines a method for the sizing of functional user requirements. The standard includes non-functional categories for data operations, interface design, technical environment, and architecture software. It includes steps to determine and calculate the non-functional size. It explains how to handle requirements involving both functional and non-functional requirements. It covers how to apply non-functional sizing estimates in terms of cost, project duration, and quality, and considerations of software performance in terms of productivity and quality. The combination of functional and non-functional size should correspond to the total size necessary to produce the software. This standard also describes the complementarity of the functional and the non-functional size, so that sizing both the functional and the non functional requirements do not overlap. Calculating the implementation work effort and duration of the non-functional requirements is outside the scope of this standard.