Streamlining Capacity Management with Bidirectional Conversion Between T-shirt Sizes and Points: CLI Tool "sizely"

#scrum #go #cli

Hi, I'm gr1m0h.

Recently, I introduced Scrum-like practices to my team. I mainly led the implementation and have been managing the operations.

As we progressed with our daily work, one of the challenges in sprint planning became capacity management. This is particularly difficult for SRE teams, which tend to have many interruptions such as incident response and ad-hoc requests. Because prediction is challenging, accurate capacity forecasting becomes the foundation for reliability improvement and leads to more challenging activities.

Many teams adopt T-shirt size estimation (XS, S, M, L, XL, etc.), but we faced the challenge of difficulty in quantitative analysis such as "How much work did the team actually complete in the previous sprint?" and "How many tasks can we plan for future sprints?"

To solve this challenge, I developed a CLI tool called sizely.
https://github.com/gr1m0h/sizely

Development Background: Why was sizely needed?

The trigger for development was when I felt that sprint planning facilitation wouldn't go smoothly if I couldn't quickly convert between T-shirt sizes and points while organizing the agenda for Scrum events.

Even when told "We completed S×3, M×2, L×1 this sprint," it's difficult to estimate a similar workload for the next sprint. Tasks of the same size don't necessarily have the same priority. Additionally, we need to consider not only team capacity but also individual capacity. The amount of work that can be executed varies depending on vacation time, on-call duties, meetings, etc., so we need to convert to points to understand capacity.

In planning communication, "L×2 + M×2 + XS×3 combination" is more concrete and easier to understand than the numerical value "33 points worth of work possible in a sprint," making task selection smoother.

sizely Features and Usage

It provides the following features:

T-shirt Size → Points: Calculate total points of completed tasks
Points → T-shirt Size Combinations: Suggest optimal task combinations for target points

Post-Sprint Retrospective

# Calculate total points of completed tasks
$ sizely points --data '{"xs":3,"s":2,"m":1,"l":1}'

📊 Sprint Capacity Calculation
═══════════════════════════════
XS (1pt): 3 tasks = 3 points
S (3pt): 2 tasks = 6 points
M (5pt): 1 tasks = 5 points
L (10pt): 1 tasks = 10 points
───────────────────────────────
Total: 7 tasks = 24 points

Next Sprint Planning

# Search for task combinations worth 33 points
$ sizely tasks 33

🔍 Finding combinations for 33 points (max 15 tasks)
═══════════════════════════════════════════════════
Found 12 combination(s):

1. L×3 + XS×3 = 33 points (6 tasks)
✅ Good mix of large and small tasks

2. L×2 + M×2 + XS×3 = 33 points (7 tasks)
✅ Good mix of large and small tasks
...

Conclusion

sizely is a tool that quantifies team capacity and enables more strategic sprint planning. Through bidirectional conversion between T-shirt sizes and points, it supports both past performance analysis and future planning.

Particularly for SRE teams that need to balance long-term goals of reliability improvement with short-term demands of daily incident response, quantitative capacity management is essential.

Although only minimal features are currently implemented, I expect this tool to contribute to team productivity improvement and ultimately to service reliability enhancement.