Frequently Asked Questions

Frequently Asked Questions - Sizing


I need a gearing factor for a language not listed on the Function Point Languages Table.  Is this information available from QSM?  What are my options if QSM does not have this information?

Although the Function Point Languages Table is fairly extensive, we do not always have enough information to provide gearing factors for every language. Before we can use a completed project in our Gearing Factors table, certain conditions must be satisified:

  1.  The project must be sized in function points.  Although thousands of projects in our database are sized in function points, we are starting with a subset of a subset of the database.
  2. The project must be recent.  Because coding techniques and languages change over time, we would not want to include projects that were 20 years old.
  3. The project must be developed in a single language or the requested language must comprise at least 80 to 90% of the project.  These days, however, it’s not uncommon for projects to be developed with a mix of technologies and languages. A project that contains only 20% Oracle  should not be used to determine an Oracle gearing factor.
  4. There should be a decent sample size.  A large sample size gives more reliable and realistic gearing factor information than a very small sample size.

Given these constraints, if you do not see a language listed in the Function Point Languages Table,  consider using the higher level language as a starting point and adjust your risk.  For example, if you were searching for an APEX (Oracle) gearing factor but did not see that language listed in the table, you can start with the gearing factor for Oracle (or another similar language) and adjust the uncertainty on size to build an appropriate amount of risk buffer into your estimate.

If you would like to know if QSM has any information about a specific language’s gearing factor, please e-mail QSM support.

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What is the purpose of the gearing factor?

Gearing factors are used to convert projects with many different sizing units (objects, modules, or use cases for example) back to a common sizing unit: the Basic Work Unit. The Basic Work Unit represents the smallest sizing unit that is common to all projects.

This conversion is important for two reasons. First, it allows us to apply the same family of PIs (or Productivity Indices) to all projects. Second, it allows you to compare your project, whether it is sized in tables, screens, or any other sizing unit, to QSM’s industry – or your own custom - trend lines, which can be sized in a variety of size units.

In our research, we have found a strong correlation between system size and important metrics like PI, schedule, effort, and defects. For more information on gearing factors, download our free whitepaper.

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SLIM-Estimate Sizing