What are story points and why use relative estimation?

Question

Accepted Answer

Story points are a **unit of relative size** that captures how much effort, complexity, and uncertainty a backlog item carries — *not* how many hours it takes. Teams estimate by comparing items to each other rather than predicting exact durations.

## How it works

Pick a small reference item as "2 points," then size everything relative to it. Many teams use a Fibonacci-like scale because bigger work is inherently more uncertain:

```text
1, 2, 3, 5, 8, 13, 20  →  gaps grow with uncertainty
```

Add up the points completed each Sprint to get **velocity**, which forecasts future capacity.

## Concrete example

"Add a logout button" is clearly a 2. "Build SSO login" feels much larger and riskier, so the team calls it an 8 — about four times the effort of the logout button.

## Common pitfalls

- Converting points directly to hours, which defeats the purpose.
- Comparing one team's velocity to another's — points are team-relative.
- Estimating huge items at "40" instead of splitting them into smaller stories.

## Why it matters

Relative sizing is faster and often more accurate than hour estimates because humans compare better than they predict absolutes.

Stable points feed velocity, which lets the team forecast realistically without committing to fragile hour-by-hour estimates.