Below is a utility to help you calculate your diet needs using BMR which stands for: Basal Metabolic Rate. This is also known as your Resting Metabolic Rate. The result of this diet calculation is only to be used as a guideline to help you caclulate you daily dietary caloric requirements.
This diet calculator DOES NOT account for any activity. So if you are even lightly active, you need to account for this in your calories.
A safe weight loss or weight gain target should be 1-2lbs per week. 1lb equals roughly 3500 calories. So, to accomplish this you will need to reduce or exceed, depending on your goal, your daily calorie intake. For example, if your BMR is 2000, and you do NO ACTIVITY, then you need to eat 1500 calories per day CONSISTENTLY to lose 1lb per week. Again, you must account for any and all activity.
Please always check with your doctor before starting any diet or exercise routine.