The relationship between the size of software and the effort required to produce it is called productivity.
For example, if a software engineer has built a small web-based calculator application, we can say that the project effort was 280 man-hours.
Conversely, we can say that the application size is 5,000 LOCs (Lines Of Code), or 30 FPs (Function Points) without identifying the project effort required to produce it.
Historically, the most common software sizing methodology has been counting the lines of code written in the application source.
The SNAP model consists of four categories and fourteen sub-categories to measure the non-functional requirements.