How to Calculate How Many Calories I Should Eat

Understanding how many calories you need in a day and not exceeding that amount is vital to maintaining, gaining or losing weight. Know how to calculate your caloric needs based on your age, activity level and body type.

The U.S. Food and Drug Administration Estimated Daily Calorie Needs table is an easy-to-use calories-per-day calculator. Infants and toddlers under three years old need the fewest calories per day, at about 1,000. As humans mature, though, caloric needs can vary by as much as 600 per day, based on biological age and activity level.

Caloric needs rise steadily throughout adolescence and peak at 19 to 20 years old for sedentary males. A young adult who does nothing more than play video games and go to school still needs to take in 2,600 calories to maintain his weight.

Highly active kids such as those involved in a swim team, track or other energetic sport require the most calories when they are high school age, from 16 to 18. The FDA recommends 3,200 calories for these kids, as compared to 2,800 for moderately active boys of the same age.

‌Read more:‌ Calories, Weight and Height According to Age

Men need to maintain high caloric input during their working years, when they are intensely physically active, consuming around 3,000 calories per day. As men reach their 40s, testosterone levels begin to decrease by 1 to 2 percent per year, according to Harvard Health Publishing, translating into potential weight gain when eating the same number of calories.

The FDA's Estimated Daily Calorie Needs chart recommends that men start scaling back their caloric intake by around 200 calories, per day if they are highly active beginning at age 36. Less-active men should begin at age 41.

Sedentary women need the most calories — 2,000 —when they're in their prime childbearing years, from 19 to 25. By contrast, highly-active females, such as those involved in competitive athletics, require 2,400 calories daily from the onset of puberty — around age 14, according to the FDA's chart — until age 30. After that, the calorie requirements taper off to 2,200 until age 60. At the onset of menopause, the caloric needs drop again, to 2,000 calories a day.

‌Read more:‌ Calorie Distribution in a Meal Plan

The FDA's recommendations are, of course, based on an average person of each age range. Chances are, you don't fit the stereotype. Your bone structure might be more massive, or your muscle mass denser, for example.

One way to get a closer estimate of your caloric need is to determine your basal metabolic rate (BMR). This is the amount of energy, in calories ,that your body requires while resting, about 60 to 70 percent of your daily needs. Use the Harris-Benedict Formula to determine your BMR.

For men:

1. Multiply your body weight in pounds by 6.3, then add 66.
2. Multiply your height in inches by 12.9. Add it to the result from step 1.
3. Multiply your age in years by 6.8 and subtract it the result from the number you arrived at in step 2. This is your BMR

For women:

1. Multiply your weight in pounds by 4.3, then add 655.
2. Multiply your height in inches by 4.7 and add it to the result from step 1.
3. Multiply your age in years by 4.7 and subtract that from the result obtained in step 2. This is your BMR.

Since your BMR is just the number of calories your body uses while resting, you now must determine the total calories you need for the entire day. Do a little more math based on your activity level during the average day.

1. Sedentary: If you go to work, sit at a desk and then come home and sit on a couch, multiply your BMR by 1.2.
2. Light Activity: If you take walks or do other light exercise one to three days a week, multiply your BMR by 1.375.
3. Moderate Activity: Play sports or exercise three to five times per week? Multiply your BMR by 1.55.
4. Intense Activity: If you're involved in competitive sports training, laborious gym exercise or other intense activity six to seven days per week, multiply your BMR by 1.725.
5. Extreme Activity: Should you train two times a day nearly every day of the week, or if you exercise or train and have a physically demanding job, multiply your BMR by 1.9.

The American Council on Exercise (ACE) also provides a daily caloric needs estimate calculator. ACE also has a physical activity calorie calculator that can help determine how much your physical exercise regime burns, based on your individual body weight.