Choosing the Right Sprint Length

One of the most common questions facing teams that are new to Scrum is "What's the best sprint length for us?".  Although this question can seem daunting at first, there's actually a simple way to arrive at the right answer for your team.

The Scrum Guide places an upper limit of one calendar month on sprint length.  And although there is no “official” lower limit, 1 week is most commonly accepted as the shortest duration that a sprint can last and still be effective.  This gives us a window of 1 week to 1 month for valid sprint durations.

So, how do you find the length that's best for your team?  The simple answer is that the best way is to experiment until you find the length that allows your team to deliver in the most predictable manner.

Beginning the Experiment

To begin, start your team running in 2 week sprints and continue this length for a few sprints.  If you find that your team either consistently misses their forecasted velocity or that they’re often unable to hit the sprint goals set out at the beginning of each sprint due to unexpected developments during your sprint, then your sprints may be too long.  In response, try shortening your sprints to 1 week in duration to see if they’re able to more consistently meet their forecasted velocity and deliver their sprint goals.

On the other hand, if you find that your team consistently meets their forecasted velocity and delivers their planned sprint goals but they struggle to make meaningful progress on the product in each sprint, then your sprints may be too short.  This is a common problem that can affect teams working in very complex domains where significant time is required to advance the product in meaningful increments.  If this sounds like your situation then experiment with lengthening your sprint to 1 month to see if that better enables your team to deliver a meaningful increment each sprint.

And, of course, if neither of these problems seem to be afflicting your team then you’ve likely discovered that a 2 week duration is just right for your team.

Tuning the Sprint

A general rule of thumb when working with Scrum teams is that it usually takes 4 sprints for a team to fully assimilate any new practice or behavior.  If after 4 sprints a team is still struggling with a new practice, then it’s unlikely that the team will ever find success with that practice.  This is often more of an indication that the practice simply doesn’t fit with how the team works best rather than a reflection on the team, themselves.

We can apply the “4 Sprint Rule” in this context, as well.  If a team has found the sprint length that’s right for them then by the 4th sprint their velocity should have normalized to the point where it can be reasonably well forecasted and they should have established a history of successfully delivering their stated sprint goals.

Knowing When Good is Good Enough

Once a team reaches this state the time that they invest in process improvement will be better spent exploring ways to improve the work that happens inside of the sprint itself, rather than continuing to invest in tuning the sprint’s overall length.  Although there is a tendency with new Scrum teams to want to continuously evolve towards shorter and shorter sprints teams should be wary of falling into this trap.

Continuously changing sprint lengths can wreak havoc with a team’s velocity forecasts making longer term planning unnecessarily difficult.  The effects of these changing sprint lengths are often not as simple as a “a team who delivers 50 points in a 2 week sprint should deliver 25 points in a 1 week sprint, or 100 points in a 1 month sprint”, therefore changing the sprint duration often requires several more sprints of observation to see where the team’s new “normal” velocity lands.It’s not out of a question for a team to begin a new project that has a high amount of unknown using 1 week sprints before eventually transitioning to 2 week sprints as the project becomes more stable.  However, such duration changes should not be taken lightly as they can have significant impacts on a team’s overall cadence.

Discovering the optimal sprint length for your team may take time but will significantly improve the team’s overall performance.  Make the investment in finding the sprint length that best suits your team and encourage the team to stick with that length once they’ve found it.