There's a formula for that, or should I say series of formulas to make it easier. I'm sure there are many out there to figure out what your caloric intake should be. This is what I use:
1. Calculate your Resting Metabolic Rate (RMR): Your current body weight x 10 = RMR
2. Calculate your Daily Activity Burn (DAB)
4. Subtract or add your Caloric Deficit (CD) or Surplus. This is the number of calories you'd like to cut out (or add) of your current diet in order to lose (or gain) weight. A good number is +/- 500 calories to gain or lose a pound a week.
5. Put them together:
RMR + DAB + DE - CD = Your Calorie Target
Write it down! You're diet and nutrition will be more effective and complete if you write it down. You won't have to wonder. Measure and weight out your portions too. You'll get it accurate. Nutrition is a science, treat it that way!
Don't forget to recalculate as you lose or gain weight! As your weight changes, so does your calorie target. Your activity level may also change as you feel better and change your lifestyle. Look at all factors separately when re-calculating. And, do it about every 3-4 weeks.
Eat smaller amounts more often to boost your metabolism and lose weight more effectively. You need to eat every 2-3 hours! Eat breakfast within an hour of waking and eat at least 3 hours before going to bed.
Keep Snacking AND Drink plenty of WATER!