Who is ultimately responsible for estimating Product Backlog items?

The Development Team is ultimately responsible for estimating Product Backlog items because they possess the technical expertise and understanding required to assess the effort involved in completing each item. The Scrum framework emphasizes the importance of the Development Team's self-management and accountability, allowing them to determine how much work they can realistically take on in a Sprint based on their capacity and skill set.

In Scrum, the Development Team engages in collective discussions to evaluate the complexity and effort of backlog items, using techniques such as relative sizing or story points. This collaboration ensures that the estimates are well-informed and reflective of the team's capabilities and experience. By empowering the Development Team to take ownership of estimation, Scrum fosters a culture of collaboration and shared responsibility, which contributes to effective Sprint planning and the delivery of valuable increments.

While others in the organization, including the Scrum Master, Product Owner, and stakeholders, play important roles in the Scrum process, the actual estimation of Product Backlog items is a task best suited for the Development Team, as they are directly involved in the execution of the work.