If you want to estimate your caloric needs there are several methods you can use. You can determine your basal metabolism using something like the Harris-Benedict equation and then add on your daily exercise activity.
Alternatively, you can use the calculator below, which simply uses your age, weight and an approximate overall level of activity to determine your caloric needs.
Which is more accurate? It's debatable and will vary from person to person. The best way to use these tools is as a starting point for a fat loss or weight gain program. Based on your results you can raise or lower your caloric consumption.