Important
Please read the previous post explaining this model, before reviewing the example below.
This example uses the following steps.
- Adds employee salary, benefits and contractor fees as cost variables.
- Calculates how much these variables cost each week.
- Sets highest number of story points burned down during a sprint as benchmark.
- Multiplies the weekly cost of the sprint by the length of the sprint.
- Divides that sum by the number of story points, revealing the cost per sprint based on actual throughput.
- Based on throughput of past sprints, creates data to calculate the cost of future sprints.
Step One:
- Sum up cost variables
- Calculate how much variables cost per week.
| Category | Yearly Salary | Yearly Benefits | Headcount | Total Compensation |
|---|---|---|---|---|
| Average Employees Developers | $97,000 | $30,361.00 | 5 | $636,805.00 |
| Average Employees QA | $97,000 | $30,361.00 | 0 | $0.00 |
| Average Contractor Developers | $97,000 | 3 | $291,000.00 | |
| Average Contractor QA | $83,000 | 4 | $332,000.00 | |
| Average Contractor PM | $98,000 | 1 | $98,000.00 | |
| Employee Benefits* | 31.3% | |||
| Salary Weeks** | 50 | |||
| Yearly Total | $472,000.00 | $60,722.00 | 13 | $1,357,805.00 |
| Weekly Total | $9,440.00 | $1,214.44 | 13 | $27,156.10 |
Step Two:
- Multiply the weekly cost of the sprint by the length of the sprint.
- Divide that sum by the number of story points, revealing the cost per sprint based on actual throughput.
- Based on throughput of past sprints, the model creates data used to calculate the cost of future sprints.
| Sprint ID | Total Weeks | Total Story Points | Total Operating Expenses for Sprint | Expense Per Story Point | Total PBI’s | Expense Per PBI | Throughput Reduction |
|---|---|---|---|---|---|---|---|
| 11 | 3 | 168 | $81,468.30 | $484.93 | 62 | $1,314.00 | -31.43% |
| 12 | 3 | 245 | $81,468.30 | $332.52 | 68 | $1,198.06 | 0.00% |
| 13 | 2 | 55 | $54,312.20 | $987.49 | 49 | $1,108.41 | -77.55% |
| 14 | 3 | 153 | $81,468.30 | $532.47 | 30 | $2,715.61 | -37.55% |
| 15 | 3 | 97 | $81,468.30 | $839.88 | 31 | $2,628.01 | -60.41% |
| 16 | 3 | 63 | $81,468.30 | $1,293.15 | 21 | $3,879.44 | -74.29% |
| 17 | 3 | 167 | $81,468.30 | $487.83 | 49 | $1,662.62 | -31.84% |
| Total Weekly Cost | $27,156.10 | ||||||
| Maximum Throughput | 245 |
The example above shows total backlog items closed during the sprint and their costs. Story points are used as a measure of throughput because they represent the lowest common denominator.
Inventory – another critical number
This example focuses on the cost of production as it responds to gains in throughput. Understanding the cost of inventory and how to manage this inventory is likewise important. If for example, a requirement or design is never built because consumers don’t want it, the value of that inventory is zero. The entire cost of that effort is lost.
Critical numbers, readily available using the Scrum Framework, should give you a clear financial overview of your project.
- Throughput (Story Points or, if it is more helpful, PBI’s)
- Operating expenses (salaries, equipment, etc.)
- Inventory a.k.a Intellectual Inventory (Backlog items or prototypes, requirements, design documents, etc. not in backlog. Making sure all items are in the backlog, ensures costs for effort do not remain unreported and the Scrum principle of transparency is maintained.)
Don’t Forget Cost of Quality
Throughput improvements should come by implementing goals during the retrospective, not by becoming more sloppy. Subtract the effort each new bug takes from the total points for the sprint; rightly increases the cost. This may be an interesting way to introduce greater quality awareness.
Final Tip From Lean
If you discover your retrospectives are not having the desired effect on efficiency, do a quick review using these five points of Lean. These may help.
- Identify the system’s bottle neck(s)
- Decide how to exploit the bottlenecks.
- Subordinate everything to the above decision (Make everything march to the “tune” of the bottleneck.)
- Elevate the system’s bottlenecks. (Improve capacity at the bottleneck.)
- If in a previous step a bottleneck is broken, go back to step one. (If the system begins to breakdown, reevaluate these five steps.)
Worksheets with formulas
Feel free to download, use and improve this model.
- Apple Numbers – Price Per Story Point
- Microsoft Excel – Price Per Story Point
Resources used to create this example:
- Agile Scrum: eliminate “intellectual inventory” using Just-In-Time software development
- How to Manage the “7 Wastes” of Agile Software Development
- Additional important terms and concepts
- Agile Estimating and Planning by Mike Cohn