Your Sprint length depends on two forces:
1- The level of changes in your market and context:
It means if your environment constantly changes, you need shorter Sprints to have more inspection and adaptation. For example, when you use one-week Sprints, you can adapt to the latest changes more frequently.
2- The ability of your Developers to build Done Increments:
If your Developers need more time to build something deliverable, then you need longer Sprints.
So, your Sprint length is a balance between those two forces.
Let’s check this table:
If your environment is highly changing and your Developers are fast to build Done Increments, then one-week Sprints are recommended.
If your environment is highly changing, but Developers are slow to build Done Increments, then the recommended length is 2-3 week Sprints.
If your environment is low-changing, but your Developers are fast to build Done Increments, again the recommended length is 2-3 week Sprints.
Finally, if your environment is low-changing and Developers are also slow to build Done Increments, then go for one-month Sprints.
Bear in mind, this is just your starting point. After running several Sprints, check the length again based on your lessons learned and tune it if needed.
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