Try the Basal Metabolic Rate calculator at BuildingMuscle.org for yourself.
Here is what the BMR calculator estimated for me to lose weight given my vital stats and a moderate level of activity as of 20140117. Although I’m actively doing yoga four or five times per week at this time I’ll be conservative and indicate the lower amount of activity. This way I’ll be sure to be eating less than needed to maintain the current body weight/mass body fat ratio.
As you can see the BMR calculator has estimated 2,934 to 3,094 Calories (kcal) per day for my body to lose body mass. Using this as a guild line I can plan the meals for each day to be within this rage or close to it. As feedback monitoring my body mass each and plotting it will enable me to see the rate of loss this amount of food has on my actual body and activity levels, this enables me to adjust appropriately for a faster burn or to increase the food if the rate of loss is too great.
One of my former medical doctor told me to “do whatever you can to lose one pound per day; seven pounds is the maximum medically safe amount per week“. Your rate of loss should be at your own rate and under medical supervision.