
Three magic Function Point Analysis formulasThe last thing I'm going to share here are three things I refer to as ``magic formulas'', mostly because I don't know how the authors of these formulas arrived at them. I'll have to assume that they had some data at their disposal, and came up with these formulas to match their data. Project Duration The first formula is credited to Barry Boehm. The formula states that the duration of a project is equal to 2.5 times the cube root of the work months, or: Project Duration = 2.5 * (Cube Root of Work Months) where Work Months is defined as Work Months = (Project Work Effort (Hours)) / (Hours per Month) So, if a project is estimated to take 27 work months, then the project duration can be expected to be Project Duration = 2.5 * (3) or 7.5 months. Optimum Staffing Size The origin of this formula is currently unknown, but it goes like this: Optimum Staffing Size = Square Root of Work Months Here, the square root of 27 is 5.2. Minimum Duration The last magic formula states that the minimum duration of a software project is: Project Duration = 0.75 * (Cube Root of Work Months) In my example, this yields 0.75 * 3, or 2.25 months. Summary How does this compare to what I've measured? In my earlier example I stated that we worked 540 manhours 10 weeks. At 160 manhours per month, this is 3.375 months. Applying the three magic formulas I would arrive at these numbers:
Before using any of these ``magic formulas'' in practice, you might try reverseengineering them like this against your own projects, and see if they work for you.
