Planning and estimating are important parts of Agile methodologies. Estimating aproject or sprint backlog for Agile teams is often quite challenging but there are many benefits of doing accurate estimations. Teams do not want to spend too much time esti-mating backlog items and are usually doing this by adopting methods such as planning poker. To estimate the size of the sprint backlog, the amount of work required for eachitem needs to be set, and also what pace the team is working with (Velocity) must betaken into consideration. This thesis is about finding guidelines for developing a tool toassist with sprint planning and to ease planning decisions such as how much work shouldbe included in each sprint and what kind of metrics should be visualized for influencingthe Scrum team and to increase team efficiency. The planning tool was evaluated byconducting user studies and collecting data from several sprints across different Scrumteams. The conducted user studies show that many teams did become more efficient byusing the planning tool. Although more extensive research would have to be made tofurther support this claim.