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Project Velocity

 
The project velocity (or just velocity) is a measure of how much work is getting done on your project. To measure the project velocity you simply add up the estimates of the user stories that were finished during the iteration. It's just that simple. You also total up the estimates for the tasks finished during the iteration. Both of these measurements are used for iteration planning.
During the iteration planning meeting customers are allowed to choose the same number of user stories equal to the project velocity measured in the previous iteration. Those stories are broken down into technical tasks and the team is allowed to sign up for the same number of tasks equal to the previous iteration's project velocity.
This simple mechanism allows developers to recover and clean up after a difficult iteration and averages out estimates. Your project velocity goes up by allowing developers to ask the customers for another story when their work is completed early and no clean up tasks remain.
A few ups and downs in project velocity are expected. You should use a release planning meeting to re-estimate and re-negotiate the release plan if your project velocity changes dramatically for more than one iteration. Expect the project velocity to change again when the system is put into production due to maintenance tasks.
Project  velocity  is  about  as  detailed  a measure as you can make that will be accurate.
Don't bother dividing the project velocity by the length of the iteration or the number of people. This number isn't any good to compare two project's productivity. Each project team will have a different bias to estimating stories and tasks, some estimate high, some estimate low. It doesn't matter in the long run. Tracking the total amount of work done during each iteration is the key to keeping the project moving at a steady predictable pace.
The problem with any project is the initial estimate. Collecting lots of details does not make your initial estimate anything other than a guess. Worry about estimating the overall scope of the project and get that right instead of creating large documents. Consider spending the time you would have invested into creating a detailed specification on actually doing a couple iterations of development. Measure the project velocity during these initial explorations and make a much better guess at the project's total size. XP Rules

Project Velocity

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