As a general rule 1500-2500 calories would be sufficient for the general population but the amount of calories you should be eating in a day would be determined by many factors. It really depends on your current body composition and where you want to go from there. For example, are you looking to lose weight? Bulk up? Are you an endurance athlete? Strength or speed athlete? Are you at a healthy body weight and looking to maintain? These are just a few variables that could be taken into account which could put you well above or below the amount of calories which would be sufficient for the general population.