Software Cost Estimation With Use Case Points – Free Excel Spreadsheet
We just completed a series of articles detailing how to use Use Case Points for software cost estimation. In this article we have a free MS Excel Spreadsheet for calculating use case points. Download it today to make it easier to do your project cost estimations.
Free Excel Spreadsheet Download
Download the use case point spreadsheet (zipped) for free today from Tyner Blain.
Background
This is the seventh article in a series on applying use case points to create reliable software cost estimates. What makes use case points different is that they allow the project cost estimation to happen much earlier in the process. This cost estimation technique was developed by Gustav Karner for Rational Software Corporation in the mid 1990’s.
The introduction to software cost estimation is the right place to start if you came to this article first. In the previous articles we discussed:
- Technical Factors of the Implementation. Characterizing (non-functional) requirements of the software.
- Environmental Factors. Describing the team and the process.
- Use Case Quantity and Complexity. Representing what the software is asked to accomplish.
- Actor Quantity and Complexity. Enumerating the users of the software.
- Final Calculations. Doing the math.
The free excel spreadsheet in this article will do the math for you. It provides an easy way to organize (and edit) your estimates, and presents the final calculation results for you.
Using the Use Case Points Spreadsheet
The spreadsheet has five tabs, one for each area of data collection and processing. The tabs map directly to the individual articles in the series (linked above). Each tab also includes links back to the articles for future review.
To calculate the use case points, you only have to fill in the highlighted (yellow) cells in each tab of the spreadsheet. All of the math is done for you.
UCP Technical Complexity Factors
Enter the relative magnitude of each technical factor. Brief descriptions of each factor are included for quick reference.
UCP Environment Factors
Enter the relative weightings of the environmental factors for the project. Brief descriptions are included for reference.
UCP Use Case Analysis
Enter the names and complexity of each use case.
Note that the complexity values are selected from a drop-down instead of being typed in. This allows for automatic calculation, just from listing the use cases.
UCP Actor Analysis
Enter the names and types of all actors that will use the system.
The actor analysis section also uses a drop-down to select the type of actor.
UCP Final Calculation
Return to the final calculation tab at the front of the spreadsheet.
All of the work has been done for you. If you want to use a different ratio for converting from use case points to hours of effort, just change the highlighted value.
Conclusion
This concludes our series on software cost estimation with use case points. With this free excel spreadsheet, you don’t have an excuse for not calculating the use case points on your project. The time you will invest is minimal. The value may be substantial.
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August 5th, 2008 at 8:25 am
How can the ratio number be defined ?
What kind of information should I base it on ? I don’t understand it. How did you come up with 28 ?
August 5th, 2008 at 10:35 am
Rodrigo, great question, and welcome to Tyner Blain.
The ratio – 28 hours per use case point, is a realistic, but otherwise arbitrary number. It can absolutely be changed.
Here’s the approach I suggest.
1) Estimate use case points for your project.
2) Use a ratio, say 28, as a “best guess” to project estimated hours
3) Track the hours spent on the project.
4) Use the actual value (from 3) and the estimate (from 1) to compute an updated ratio.
5) Use the updated ratio, for your team, for your next project, and repeat steps 1-4.
You should also review to determine if your estimates (per 1) were off, and include that feedback loop so that you get better estimates of the number of use case points. Over time, your ability to estimate / predict will improve.
October 1st, 2008 at 1:41 am
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November 24th, 2008 at 3:23 am
[...] Case Estimation spreadsheets are available on the Internet and the expression of the activity itself is well suited to a [...]
January 6th, 2009 at 7:04 am
[...] estimations for real world projects and in so doing I will be able to remove the dependence on the spreadsheet that currently manages this task for me. As it stands today, the project details tab has it’s [...]