There are two routes to estimating software development effort for a project:
Estimate the software size and arrive at the effort required to develop the software for the project using this software size estimate.
Directly arrive at the effort required to develop software for the project.
To arrive at an effort estimate from a size estimate, we use a productivity figure. A productivity figure expresses the rate of achievement. The rate of achievement can be expressed as person-hours per unit of software size or as software size per person-day. ...