In order to find out how many calories a man (or woman) needs, all you do is take your weight in pounds and multiply that by 15.
So if you weigh 150 pounds, that would be 150x15 = 2,250 calories/day.
This is a good rough estimate.
If you're looking to lose weight and not just maintain, you would eat at least 500 calories below this number each day. That would create a weekly 'deficit' of 3,500 calories which is the exact amount of calories you need to burn to lose 1 pound of fat!