Demystifying Software Project Estimations Using Function Points

Saurabh Saxena has 11 years of IT experience, the last seven of which he has specialized in software sizing measurement and estimations using function points. He is a Certified Function Point Specialist (CFPS) and Project Management Professional (PMP). The International Function Point User Group (IFPUG) has appointed Saurabh as Function Point India Representative (POC for India region). He is a major contributor to several software sizing manuals, white papers and trainings. He is also part of the IFPUG task force for any function point-related initiatives around the world.

  Business Intelligence   Complexity   Estimating   Information Technology   Requirements Management   Scheduling   Strategy  

How do you correctly estimate software projects? This quandary has often left most project managers perplexed, causing multiple project failures.

Effective software project estimation is one of the most challenging activities in software development. Proper project planning is not possible until a sound and reliable estimate is available. Software effort estimation is the process of predicting the most realistic amount of effort required to develop or maintain software based on initial high-level requirements. Effort estimates are then used as input to project plans, resource loading, scheduling, budgets and pricing processes.

Underestimating a project leads to under-scoping, under-staffing and setting too short a schedule. Similarly, generously padding the estimate and overestimating is equally bad. It causes increased cost, longer schedule to deliver and superfluously blocks the allocated resources in the project.

The four basic steps in software project estimation are:

1. Estimate the size of the project using standard methodology (function points)
2. Translate the project size into efforts (person-months/person-hours)
3. Calculate the schedule in calendar months
4. Estimate the project cost (dollars or local currency)

1. Estimate the size of the project using IFPUG function points
A person …

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