That’s a tough question. You will be able to find sprint length recommendations ranging from 1 week to 2 months. The ideal length depends on:
Overall Length of the Release: Short projects benefit from short iterations.
Amount of Uncertainty: The more uncertainty of any type there is, the shorter the iterations should be.
How Long Priorities Can Remain Unchanged: Once a development team commits to completing a specific set of features in an iteration, itâ€™s important that they not be redirected from that goal, so people outside the team shouldnâ€™t change the teamâ€™s priorities during an iteration.
The Overhead of Iterating: Costs are associated with each iteration.
How Soon a Feeling of Urgency Is Established: The intensity level varies quite dramatically on a twelve-month, non-iterative, waterfall-process project.
As explained by Mike Cohn in his post “Selecting The Right Iteration Length For Your Software Development Process“.