They aren’t absolute measurements like hours or days but measure the amount of work a PBI takes relative to other PBIs. Typical measurements include using Fibonacci numbers or t-shirt sizes.

Learn to use story points and explore the essential Scrum glossary.

In Scrum, you are not measuring work in absolute terms like hours spent or lines of code to be written. Two reasons for this:

1. Not everyone works at the same pace or has the same set of expertise and experience.
2. Until you do the job, these are unknown and, at best just guesses.

The problem with absolute sizing using hours is you begin to measure the people, not the work. Relative sizing measures the new work against past work shared by the whole team. Instead, the work is sized relative to past work already completed. So when looking at a new user story, the team asks, “Is this user story A most similar to this past user story B or this past user story C?”

Learn other essential Scrum terms.

The Fibonacci sequence is the go-to solution for many Scrum teams because it allows for relative sizing while still being a numeric measurement. It has two key advantages:

1. Keeping story points measured in numbers is advantageous because it is then easier to calculate a team's velocity.
2. The numbers have distinct relationship with each other making relative sizing more intuitive. The Fibonacci sequence increases such that each number is the sum of the previous two number.

Non-numeric options are still possible, and one of the most popular is using t-shirt sizing, like small, medium and large. Lean more about using story points or learn other essential Scrum terms.

This measurement allows the product owner to forecast when future features will be ready. It is calculated by averaging how many points the team has complete over the past few sprints.

Learn to forecast in Scrum using velocity and explore the essential Scrum glossary.