You could use WedgeDawgs applicant rating system as a starting point, it'll give you a suggestion as to how many reach/match/safety schools you apply to. Keep in mind though that the lines between the three are very fuzzy, you'll get differing opinions as to whether a given school should be considered a reach vs a match for your stats. It also depends on how much money you're willing to dole out on apps. If you're tight on funds, probably want to limit yourself on reaches, but if you've got money to burn, throw in some more.