The Science of Estimating for Software Development
The last two years of my life have been split between managing a development team and actively doing development for our clients. In the management role I spend a LOT of time providing estimates for software development. More specifically, functional consultants write up design documents for features our clients ask us to build. The first thing our clients need and want from me is an estimate for how many hours the development work will take to complete. With the estimate in hand the client can decide whether or not they want to proceed. Contrary to popular opinion, I have found there is a way to provide an estimate that closely approximates what the actual number of hours will be. Estimating does not have to be an art, it can be a science. My approach is simple. It involves taking some time during the estimation phase and using specific actions to remove the guess work.
My Estimating Approach:
1. Understand the Design
When given a design, the first step is to make sure I understand the design. If I don’t understand what tasks are in the design I talk it over with the functional consultant until I fully grasp what I need to build. This first step can take a while but it is the most important step.
2. Breakdown Tasks
Once I know what I’m building, I break the design down into the tasks that comprise it. For example, if one of the pieces of the feature involves building a setup form, my list of tasks will look like:
a. Create a table
b. Create a form that uses the table
c. Create a menu item to point to the form and add the menu item to a menu
d. Create a privilege so security can be granted to the menu item
e. Test the form from the menu
3. Assign Hours to Tasks
With the list of tasks in front of me, I assign an hourly estimate to each task.
4. Look for Red Flags
A single task with an estimate of more than 20 hrs is a RED flag. It means the task is not straight-forward and that I need to research it some more. I give myself up to 2 hours to think about that particular task in more detail. Once I feel more comfortable, I break that one task down until I have the components of it included in my task list.
5. Assign Estimate to Each Task
With the further broken down task list, I make sure each task has an estimate.
6. Add Details to Functional Design
Once my tasks and their estimates are complete, I add all of those details to the functional design. With all of the details in the design my client, the functional consultant and I know exactly what I was thinking at the time I gave my estimate.