According to Wikipedia, it is recommended that there should be a four hour meeting in a two-week sprint planning (pro-rata for other sprint durations).
Is it necessary? Why?
I'm going to slightly disagree with Bogdan's answer.
The Scrum Guide does say that:
Sprint Planning is time-boxed to a maximum of eight hours for a one-month Sprint. For shorter Sprints, the event is usually shorter.
We normally think in weeks, so I translate "one-month Sprint" to "four-week Sprint". However, it goes on to say that if the Sprint is shorter than 4 weeks, "the event is usually shorter". The Scrum Guide does not give a suggestion on how to scale the timebox for an event for shorter Sprints, nor does it even say that the timebox needs to be scaled for shorter Sprints.
Common advice is to scale linearly. That is, if a Sprint with a timebox of 4 weeks has a timebox of 8 hours for Sprint Planning, a Sprint of 2 weeks would have a timebox of 4 hours for Sprint Planning. In my experiences, this works out well for scheduling purposes. It is important to keep in mind that a timebox is a constraint, not a mandatory duration - the event ends when its intention has been fulfilled and the maximum time should be the timebox.
I've found that if you spend sufficient time on Product Backlog refinement activities before Sprint Planning, then Sprint Planning will be much more efficient. The Scrum Guide recommends that approximately 10% of the Development Team's capacity be allocated to refinement, but note that this isn't a timebox - it may be more, it may be less, but it's a good guideline to keep in mind. If you go into Sprint Planning and the bulk of the work at the top of the Product Backlog is well refined and understood by the Development Team, identifying which Product Backlog Items can be done within the Sprint becomes much easier and the team can focus on developing a plan for getting that subset of items to Done.
The Scrum Guide mentions that:
Sprint Planning is time-boxed to a maximum of eight hours for a one-month Sprint. For shorter Sprints, the event is usually shorter.
If you keep the same train of thought, that translates to a maximum of four hours for a two week sprint.
Events are time boxed in Scrum so that people stay focused on the activity. Imagine if the Daily Standup wasn't time boxed, people will just talk and talk and talk. Same with the Sprint Planning, people need to stay focused to plan the Sprint. If you spend a lot of time planning and go beyond the four hours then that's a sign of possible issues (maybe someone hijacks the meeting, maybe stories aren't properly refined, maybe people are day dreaming, etc) so in normal conditions the Sprint Plannings will take less than four hours.
The four hour per two week Sprint is a maximum. It does not mandate that you spend exactly that much amount of time on the activity. If you plan properly and you finish your planning sooner, then that's no problem at all.
Four hours is way too long for a productive meeting [1]. Here's an excerpt from an article by FastCompany:
What’s your record for longest meeting?
Can anyone beat my four-hour marathon? (I bet many of you can!)
When it comes to meeting pain points, length often tops the list. How is it that meetings tend to go on so long, sometimes (OK, many times) unnecessarily? Here’s an old project management adage that might explain it:
Work expands to the time you schedule for it.
For this reason, you may want to keep meetings to 15 minutes or shorter, whenever possible. Yahoo’s Marissa Mayer will schedule 10-minute meetings, out of necessity for her busy schedule. The team at Percolate sets 15 minutes as the default length for all meetings, adjusting up or down as needed. Percolate values the 15-minute default so highly, they framed it in their set of six meeting rules.
Why might it seem like 15 minutes is an ideal starting point for meeting length? For one, it’s easy to schedule in an Outlook calendar or Google calendar. Though the default in most calendar apps is 30 minutes, you can quite easily adjust down to 15-minute increments as that’s how most schedule grids are created.
For the science behind the 15-minute rule, you need look no further than a TED talk. Each TED talk is kept to 18 minutes or shorter, the same time as a coffee break and a helpful constraint for presenters to organize their thoughts. Scientifically, 18 minutes fits right in with the research on attention spans: 10 to 18 minutes is how long most people can pay attention before checking out.
The 18-minute max has physiological roots. Our bodies require a large amount of glucose, oxygen, and blood flow when the brain processes new information. Sooner or later, we feel physically fatigued.
It's true that some people (managers usually) like long meetings, but for many people long meetings 1) kill productivity by causing significant mental fatigue, 2) harm morale because they're seen as almost a form of torture, and 3) signal incompetence (I tend not to think my team knows where its going if they have to have 2+ hour meetings all the time to figure things out).
Seriously, unless you want your team to start hating you, keep meetings to a minimum and make them highly focused. It takes more work but it will 1) keep your team from getting as drained mentally; 2) keep your team happier; and 3) make your team think more highly of your organizational skills. I would seriously consider leaving any team that had regular mandatory four hour meetings, and I'm sure I'm not alone.
In my opinion, no. I once took over leadership of a team that had 4-hour biweekly planning meetings, and it was miserable. No one is effective towards the end of a 4-hour meeting, and it led to plenty of bad decisions. I was eventually able to bring it down to an average of 90 minutes (in a 2-hour slot) and the resulting work was greatly improved. The key, of course, is preparation — and, if necessary, cutting off discussion within the meeting. The backlog should be in a good state before you come into planning. If a story isn't well-defined by backlog grooming the week before, then you aren't ready to take it on. If you know what you're doing but estimation becomes a discussion about how to do it, then you need to do a confidence check. Either you decide as a team that you're discussing details which can be figured out after planning without major impact on the timeline, or you decide that there's major uncertainty in the approach, and kick the story out in favor of a research spike which will let you do it with confidence. Either way, doing the research during the planning is the worst available option.
For a team that's done minimal pre-meeting preparation, is working on a new project, and/or who are new to working together, 4 hours for a 2-week sprint seems reasonable. It's better to waste a few minutes in a meeting than waste a few days of a developer's time during the sprint because a task wasn't clear enough or if technical blockers weren't discussed during sprint planning.
That said, it's definitely possible to reduce the time required for Sprint Planning meetings without adding risk. Here's a few basic techniques that we used to reduce our average Sprint Planning meeting to less than 30 minutes per 3-week sprint for a 15-person team:
Doing all the above wasn't easy. It required a lot of discipline from everyone on the team to each do their part. But all the prep work above made Sprint Planning meetings quick. PMs would go through the Sprint Draft email they sent several days earlier, devs would ask questions about specific tasks, and we'd wrap up. After a while of doing this, we could usually finish Sprint Planning in 20 minutes.
True, there was other planning work happening outside Sprint Planning. But crucially that other planning work didn't require big blocks of time from the entire cross-functional team. So the overall efficiency of the team was improved. More importantly (for both the business and for team morale), sprints became more predictable with fewer all-nighters, fewer missed deadlines, and fewer arguments.
I would say the length of a sprint planning session depends on a number of things:
1 - If the backlog is in a bad shape, planning will take longer as you'll need to tease out the detail.
2 - If you have strict conditions, there may be some tickets up for discussion with respect to their scope, conditions of acceptance etc...
3 - Planning poker can take longer, as there is more discussion when someone pulls a 5 vs a 20.
4 - Sprint planning is usually 2 hours per week of development, but varies depending on who you ask.
5 - Are you dev heavy? Test heavy?
6 - Are they good at writing stories and conditions of acceptance? Are they aware of stakeholder priorities?
7 - Stories which are hard to automate may require further discussion.
8 - Won't really affect the length of sprint planning, but thought I'd add it in anyway.