If you want to lose weight aim to eat 500 calories less than your daily caloric needs - or burn off more calories through exercise. Ideally, combine the two. If you reduce your calories by 500 every day - perhaps by eating 250 calories less and burning 250 calories more - you will lose about one pound each week.
You can use the calculator on this page, or use the even more accurate calculator from the very good freediet.com.
Daily Calorie Requirement Calculator
Adjust sliders to get your daily calorie needs
Required Calories Per Activity Level
Little or no exercise, desk job
Light exercise/sports 1-3 days/week
Moderate exercise/sports 3-5 days/week
Hard exercise/sports 6-7 days/week
Hard daily exercise/sports & physical job or 2X day training