As others said it totally depends on the beer.
I calc for 5.5 gallons post boil for beers that don't require a lot of hops, and aren't dry hopped. That yields pretty much exactly 5 gallons into the keg/bottling bucket.
For my APAs, American ambers, IPAs, or anything with 5oz of hops or more, I calc for 6 gallons post boil.