How Many Calories Do You Need?

Everything you do — from sleeping to eating a bowl of rocky road ice cream — burns calories. Likewise, every bodily function, like digestion, blood circulation, and breathing, takes effort. The energy, or calories, your body burns just to keep you alive is called your basal metabolic rate (BMR). Also known as your resting metabolic rate, it reflects how many calories you would burn if you did nothing but lie on the floor all day.

Want to find out how many calories your body needs to survive? Use the formula below to calculate your BMR. You can then use your BMR to figure out how many calories you need each day to maintain, lose, or gain weight.

Calculate Basal Metabolic Rate

Women: 655 + (4.35 x weight in pounds) + (4.7 x height in inches) - (4.7 x age in years)
Men: 66 + (6.23 x weight in pounds) + (12.7 x height in inches) - (6.8 x age in years)

Example: You are 38-year-old woman, who is 5'4" and 142 pounds.

First, convert your height into inches. 5'4" equals 64 inches.

Now paste your values into the equation above.
655 + (4.35 x 142) + (4.7 x 64) - (4.7 x 38)
655 + 617.7 + 300.8 - 178.6 = 1394.9
Your BMR = 1394.9

Calculate Total Calorie Needs

Even the most sedentary person will burn more than that just by smiling, laughing, or fidgeting. To get a better sense of how many calories your body uses in any given day, you need to factor in your activity level. To determine your total daily calorie needs, multiply your BMR by the appropriate activity factor, as follows:

If you are sedentary (little or no exercise): BMR x 1.2
If you are lightly active (easy exercise/sports 1-3 days/week): BMR x 1.375
If you are moderately active (moderate exercise/sports 3-5 days/week): BMR x 1.55
If you are very active (hard exercise/sports 6-7 days a week): BMR x 1.725
If you are extremely active (very hard exercise/sports and physical job): BMR x 1.9

Continuing with our example, let's assume you are lightly active. Multiply your BMR from above (1394.9) by 1.375 = 1917.9875. This is the total number of calories you would need to maintain your current weight.

Calculate Calories to Lose Weight

One pound of body fat is equivalent to 3,500 calories — which means a person must cut that many calories from her diet to lose a single pound. By eliminating 500 calories a day, she will lose one pound in a week. So, if your daily caloric need is 1917.9875 to maintain your weight, subtract 500 from that, and you'll have the number of calories you can consume each day and still lose a pound in one week. In this case: 1,417.9875 calories.

Calculate Calories to Gain Weight

Likewise, to gain one pound per week, you'll need to add 500 calories to your diet each day, consuming a total of 2417.9875 calories a day.

Improving Your Metabolism

Why do you care about your metabolic rate? Your metabolism, to a large degree, determines your dieting success. You want to keep it running high to burn the most calories. Unfortunately, many things can slow it down:

Age: Your metabolism slows by 5 percent every decade
Fat: Muscle burns three times more calories than fat

Dieting: Slashing calories sends your body into starvation mode. It runs more slowly to preserve calories, because it thinks that food is scarce. This is the reason why your weight loss can plateau during a diet.

Exercise and building muscle mass through weight training, on the other hand, help to keep your metabolic rate up, which is why it is so important when dieting.