ISO/IEC/IEEE 32430

Software engineering — Software non-functional size measurement

Scope

This document specifies a method for measuring the non-functional size of the software. It complements ISO/ IEC 20926:2009, which defines a method for measuring the functional size of the software. Together, the two standards provide a method to measure the software size derived by quantifying the functional and non-functional user requirements.
Measuring the non-functional size of the software assists organizations in multiple ways. It provides insight into the delivery of projects and maintenance of applications to assist in estimating effort and analyzing quality and productivity. Used in conjunction with FSM (Functional Size Measurement), the non-functional size provides information to identify items impacting quality and productivity -  positively or negatively.
The standard provides a clear and detailed description of the sizing method:

A foundation to ensure that sizing is consistent.
The sizing process.
Formulas to calculate the software size
Guidance to handle requirements involving both functional and non-functional aspects.

The standard also provides information on how to apply the non-functional size for project resource forecasting, cost estimation, and project performance management.