A simple way to software sizing measures
There are different ways of measuring the size of software applications, such as measuring lines of code or functions points. With lines of code the size is measured after the application has been built. This approach is dependent on the technology used to build the application, its design and the programming languages used for code. Applications coded using different programming languages cannot be easily compared and this might compromise efficient code.
With function Points the size is a measure of delivered functionalities that is relatively independent of the technology used to develop the application, and it's measured from the user's perspective. Therefore, sizing the application is done by counting external data (inputs, outputs, interfaces, files and inquiries); this might not be so intuitive and difficult to communicate.
A simple way to size an application is to use a more intuitive approach. This is analogous to function points approach, but it's made more simple by using parameters in an approximative way. For example, during the analysis phase, it's possible to capture information related to the number of use cases, user interfaces, reports, rules/algorithms, and data tables needed for a particular application. Each component (i.e., each UI, each UC, each Report, etc...) is multiplied by the estimated effort needed to build it. This operation is done for all components, and a total effort is calculated and easily converted into costs.