How long is a sprint planning session? The rule of thumb is to allocate 2 hours for each week of the sprint. As sprints are 1 to 4 weeks long, a sprint planning session is from 2 hours to 8 hours long. The most common sprint length used in practice is 2 weeks and thus the most common length of the sprint planning session is 4 hours. If requirements are about to be changed more often due to the nature of the project, a shorter timescale of one week is preferable or if the team wants to gain momentum longer sprints are also acceptable such as 3 or 4 weeks. Once the sprint length is decided, it should remain constant so that the team establishes a rhythm and can track their velocity consistently across different sprints. That is why it is important to have the backlog ready for sprint planning - if there are not enough ready user stories to fill the sprint, it is not acceptable to shorten its duration according to the ready work but instead it is needed to ensure in advance that there is enough ready backlog.