The number of calories you can eat daily depends on your individualized weight-management goals. The Dietary Guidelines for Americans 2010 estimate that women ages 19 to 50 generally need 1,800 to 2,400 calories a day to maintain healthy weights. Although these general calorie recommendations exist, you can use other methods to more precisely estimate your daily calorie needs. The most accurate way to determine how many calories you can eat to reach or maintain your goal weight is by recording everything you eat and weighing yourself regularly.
Complicated formulas exist to help determine your body’s daily calorie needs. For example, a study published in 2006 in “Preventative Chronic Disease” uses the formula 387 − 7.31 × age in years + physical activity factor × (10.9 × weight in kilograms + 660.7 × height in meters) to calculate an adult woman’s total energy expenditure -- and therefore her calorie needs for weight management. Physical activity factors for women are 1 if they are sedentary, 1.14 if they have low activity levels, 1.27 if they're active and 1.45 if a woman is very active. However, even complicated formulas are not entirely accurate.
2. Food Journals
Keeping a food journal is often the best way to determine how many calories your body is getting – and requires – daily. Record everything you eat in exact amounts in your food journal for one week. Use nutrition facts labels and online nutrition databases, such as the U.S. Department of Agriculture’s National Nutrient Database for Standard Reference, to determine how many calories you’ve eaten daily that week. Weigh yourself on day one and day seven to see if you’ve gained, maintained or lost weight and adjust your calorie intake as needed to reach or maintain your goal weight.
3. Calories per Pound
Though simply an estimate, using your body weight and physical activity level to determine your calorie needs for weight maintenance is quick and easy – and more practical than using complicated mathematical formulas. According to Harvard Medical School, sedentary women need about 13 calories per pound of body weight daily, while active adults may need up to 18 calories per pound on a daily basis. Based on these recommendations, a 130-pound woman needs 1,690 to 2,340 calories daily – depending on her activity level – to maintain her weight.
4. Weight Loss
If you want to shed pounds, it’s fairly simple to determine how many calories you should eat daily. The Centers for Disease Control and Prevention recommends reducing your current calorie intake by 500 to 1,000 calories daily to help you drop 1 to 2 pounds weekly, which is safe and healthy. You can use general weight-loss guidelines to estimate your calorie needs while losing weight. The National Heart, Lung and Blood Institute suggests inactive women weighing less than 165 pounds usually require 1,000 to 1,200 calories a day, while women weighing more and those who exercise often may require 1,200 to 1,600 calories daily to shed pounds effectively and safely.