Center for Systems and Software Engineering



COnstructive COst MOdel has a rich legacy. Originally published by Dr. Barry Boehm in 1981 under the name COCOMO, it went on to become (and arguably remains) the most widely used software project cost estimation model throughout the world. The 1981 model is now referred to as COCOMO 81.

COCOMO 81 is a model that allows one to estimate the cost, effort, and schedule when planning a new software development activity, according to software development practices that were commonly used in the 1970s through the 1980s. It exists in three forms, each one offering greater detail and accuracy the further along one is in the project planning and design process. Listed by increasing fidelity, these forms are called Basic, Intermediate, and Detailed COCOMO. The original COCOMO has also existed in other incarnations, the most prominent being Ada COCOMO.

In the ensuing two decades since 1981, software development techniques changed dramatically. These changes included a move away from mainframe overnight batch processing to desktop-based fast turnaround; a greatly increased emphasis on reusing existing software and building new systems using off-the-shelf software components; and spending as much effort to design and manage the software development process as was once spent creating the software product.

These changes and others began to make applying the original COCOMO model problematic. The solution to the problem was to reinvent the model for the 1990s. The result is COCOMO II, a revised cost estimation model reflecting the changes in professional software development practice that have come about since the 1970s. This new, improved COCOMO is now ready to assist professional software cost estimators for many years to come.


Software Engineering Economics is still the most complete resource for information regarding original COCOMO 81, as well as providing a wealth of information on the economics of software engineering that will improve one’s understanding and application of any COCOMO model.

Software Engineering Economics by Barry W. Boehm
Barry W., Boehm, Software Engineering Economics, Prentice Hall, 1981