There are several ways to calculate your calorie needs.
1. Your current weight is a direct reflection of how many calories you consume and how many you burn. Ideally, you need to know what you are currently eating before you can plan for weight loss. In short, you wouldn’t dream of beginning a trip without first knowing your starting point. A weight loss journey is the same. That means keeping a food journal. Write down everything you eat, how much, and when for at least two week days and one weekend day (people tend to eat differently on weekends). Tally the calories to find your starting point.
2. Or, you can get a general idea with another calculation method: Women between the ages of 18- and 30-years-old multiply their weight by 6.1 and add 487 for their basic calorie needs. (Women 31- to 60-years-old should multiply their weights by 4 and add 829.) Next multiply this basic number by 1.3, 1.5, 1.6, or 1.9, depending on whether you are sedentary, slightly active, moderately active, or very active, respectively.
Once you have determined your current calorie intake, cut 500 calories from this total (or add 500 calories in exercise) to lose about a pound a week (3,500 calories = 1 pound.) Another simple formula is the 100/100 Plan. To lose two pounds a month, all you need do is cut 100 calories from your daily diet and add 100 calories in exercise. This is as easy as eliminating the pat of butter on a slice of toast and walking 20 minutes every day.
3. Of course, another way to calculate is to just weigh yourself daily. You are cutting calories and exercising enough if you are losing weight (at about 2 pounds a week). If you aren’t losing weight, you need to cut more calories and/or move more.