Many commercial tools are available to help you estimate entire projects. Based on large databases of actual project experience, these tools can give you a spectrum of possible schedule and staff allocation options. They’ll also help you avoid the “impossible region,” combinations of product size, effort, and schedule where no known project has been successful. The tools incorporate a number of “cost drivers” you can adjust to make the tool more accurately model your project, based on the technologies used, the team’s experience, and other factors. Over time, you can calibrate the tool with your own project data to make it an even more reliable predictor of the future. You can compare the estimates from the tools with the bottom-up estimates generated from a work breakdown structure. Reconcile any major disconnects so you can generate the most realistic overall estimate.
Adapted from “Practical Project Initiation: A Handbook with Tools” (Microsoft Press, 2007). A condensed version of this paper was published in Software Development magazine.
Karl Wiegers, Ph.D., is Principal Consultant with Process Impact, a software process consulting and education company in Portland, Oregon. Karl’s most recent book is “Practical Project Initiation: A Handbook with Tools.” Karl is also the author of four other books and 170 articles. Karl is a frequent speaker at software conferences and professional society meetings. You can reach Karl through www.projectinitiation.com or www.processimpact.com.