Story Points
A unit of measure for estimating effort in agile development.
Detailed Explanation
Story points are a unit of measure used in agile to estimate the overall effort required to implement a user story or backlog item. They reflect a combination of complexity, effort, and uncertainty — not just time. Common scales include Fibonacci (1, 2, 3, 5, 8, 13, 21) and T-shirt sizing (XS, S, M, L, XL).
Story points are relative, not absolute. A 5-point story is roughly 2.5 times the effort of a 2-point story. Teams calibrate by choosing a reference story and estimating everything relative to it. Over time, teams develop a shared understanding of what each point value means.
The primary value of story points is enabling velocity calculation — the average number of points completed per sprint. Velocity enables realistic sprint planning and release forecasting without converting estimates to hours, which gives a false sense of precision.
Key Points
- Reflect complexity, effort, and uncertainty combined
- Common scales: Fibonacci sequence or T-shirt sizes
- Relative estimates, not absolute hours or days
- Teams calibrate with a reference story
- Enable velocity calculation and release forecasting
- Avoid false precision of hour-based estimates
Practical Example
A team uses Fibonacci story points. Their reference story ('Add a text field to a form') is 2 points. 'Build user authentication with OAuth' is estimated at 8 points (4x the reference in complexity/effort). 'Change button color' is 1 point. The team's average velocity is 30 points per sprint, so they plan 28-32 points per sprint.
Tips for Learning and Applying
Use Planning Poker for team consensus on estimates
Do not convert story points to hours — that defeats the purpose
Recalibrate periodically as the team's understanding evolves
Track velocity trends to improve sprint planning accuracy
Related Terms
Want to Master These Concepts?
Our courses cover all these terms in depth with practical examples and exercises.