You can estimate how many calories you need per day based on your age, height, gender and activity level using the Harris Benedict equation. Your calorie needs are the amount of calories you require to maintain your current weight.
If you want to lose 1 to 2 pounds a week, you need to subtract 500 -1000 calories from your estimated total daily calories.
You can calculate your daily calorie needs, by using the Calorie Calculator provided by the Mayo Clinic.