In terms of mapping story points to time ranges, here's the full list:
1 point -> 2-4 hours
2 points -> 4-8 hours (1 day or less)
3 points -> 1-2 days
5 points -> 3-5 days (up to one week)
8 points -> 5-9 days (up to one two-week sprint[0])
13 points -> 2-3 weeks (1-1.5 sprints)
20 points -> 3-4 weeks (up to two sprints)
40 points -> 1-2 months
Anything beyond 40 needs to be aggressively analyzed broken down into steps, even if those steps are not deliverable features per se.
[0]For a two-week sprint, you have to account for at least one day each sprint for demos, retrospective, and planning. Thus, you have at most 9 days for implementation and testing.
