It's Relative

Technically, there is no magic number of calories we should all eat each day to lose weight. Some people can lose weight eating around 1,500 calories other can’t. An assessment of your own personal calories can be done with a little math. All you need to assess is your basal metabolic rate (BMR). To lose weight, you'll need to cut calories or burn extra calories and shoot for a level lower than the results you get with this formula.

BMR
Your BMR is the amount of energy your body needs to function. 60% of the calories we consume each day for basic bodily functions such as breathing.
Other factors that influence your BMR are height, weight, age and sex.

BMR Formula:
Women:
655 + (4.3 x weight in pounds) + (4.7 x height in inches) - (4.7 x age in years)
Men:
66 + (6.3 x weight in pounds) + (12.9 x height in inches) - (6.8 x age in years)

Calculate Activity
Step two: In order to incorporate activity into your daily caloric needs, do the following calculation:
If you are sedentary: BMR x 20 percent
If you are lightly active: BMR x 30 percent
If you are moderately active (You exercise most days a week.): BMR x 40 percent
If you are very active (You exercise intensely on a daily basis or for prolonged periods.): BMR x 50 percent
If you are extra active (You do hard labor or are in athletic training.): BMR x 60 percent
Add this number to your BMR.

The result of this formula will be the number of calories you can eat every day and maintain your weight. To lose weight you'll need to take in fewer calories.
As you lose weight re-calculate the formula to assess your new BMR.


Calorie Deficit
In order to lose weight, you must create a calorie deficit. It is easier and healthier to cut back your calorie intake a little bit at a time. Every 3,500 calories is equivalent to one pound.
So, if you cut back 500 calories a day, you should lose about one pound per week. If you exercise to burn off 500 calories a day you should lose approximately one pound per week. You should do a combination of both, (such as cut back 250 calories; burn an extra 250 calories).
Your weight loss will vary from week to week and at times you could even gain weight -- if you're working out you could be developing muscle, and we all know that muscle weights more than fat. The long-term is what matters.

Losing
Healthy weight loss is to lose .5 to 2 pounds per week. Losing more than 2 pounds per week will mean the weight is less likely to stay off permanently. Never cut back to fewer than 1,200 daily calories without medical supervision.