A 42″ space on all sides is a good place to start. Less than that is pretty tight and while more is fine you can create to much walking between work areas. On the other hand, 48″ is a minium if two appliances are opposite each other (sink at the window and an island cook top directly behind, as?an example). Sometimes the driving factor is simply the space that is avaliable. If there is seating involved, we would need to discuss that?as well.