All You Need to Know About How Many Calories Should You Eat a Day

If you have been asking yourself, how many calories should you eat a day then you are asking the right question. Whether you are aiming to lose or gain a few pounds or want to maintain your current weight, tracking your daily caloric intake is important.

The number of calories that you should intake in a day depends on a lot of things, such as your age, gender, and activity levels. Thanks to modern science, we can now somehow determine the optimal number of calories you should be consuming based on these factors.


Activity Levels

One of the most important factors to determine your optimal calorie intake levels is your daily physical activities.

The Institute of Medicine, which has changed its name to the National Academy of Medicine, developed a series of equations that can help you determine your EER or Estimated Energy Requirement, which is an estimated number of calories needed to maintain your current weight.

However, before you can determine your EER, you will need to figure out what your daily activity level is. The Institute of Medicine breaks down activity levels into four parts.

calories per day calculator
  • Sedentary: This activity level is for people who do only light activities on most days, such as the activities needed to sustain yourself and your household. So, if you don't exercise much and are only active when you need to clean the house or do laundry, then you fall under the Sedentary classification.

  • Moderately Active: Moderately active people do half an hour of moderate to vigorous exercise each day in addition to the activities described as sedentary. 
  • Active: If you do at least an hour of exercise each day, then you qualify as active.
  • Very Active: The very active category is usually reserved for people with physically demanding jobs. And, you must be physically active for several hours each day to be classified as very active. 

EER Equations

daily calorie intake calculator

The EER equations are used by the USDA to set national standards on calorie consumption. These may seem complicated at first, but they're easy enough once you know what to fill in such as your activity level.

In this article, we are going to focus on the adult equations. If you need to determine a child's optimal calorie intake, then you can find those equations here

The EER equations for men and women are as follows:

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For Men

EER = (662 - (9.53 * age)) + PA * ((15.91 * weight) + (539.6 * height))

For Women

EER = (354 - (6.91 * age)) + PA * ((9.36 * weight) + (726 * height))

Let's go through and assign values to all those italics.

  • Age: your time of existence in years
  • PA: physical activity coefficient, which is your activity level as determined in the last section.
  • Men:
  • PA = 1 if you are sedentary
  • PA = 1.11 if you are moderately active
  • And, PA = 1.25 if you are active
  • PA = 1.48 if you are very active
  • Women:
  • PA = 1 if you are sedentary
  • PA = 1.12 if you are moderately active
  • And, PA = 1.27 if you are active
  • PA = 1.45 if you are very active
  • Weight: your mass in kilograms
  • Height: your measure from head to toe in meters

Crunch these numbers, and you'll have your estimated energy requirement in calories! 


So, we hope you have done the math for the result is your baseline. But, this number will answer your question, how many calories should you eat a day?

Your EER is the number of calories that a person of your age, gender, height, weight, and activity level needs to consume to maintain his or her current weight. If you're happy with your current weight and activity status, then great! Nevertheless, you know how much you should be consuming.

Unfortunately, for most people, the work doesn't end there. Some may want to gain or lose weight, while others have medical conditions that affect their metabolism, which change their calorie requirements.

Below are some basic guidelines on how to approach each of these issues.

Calorie Consumption for Weight Loss

The basic premise for losing weight is simple. You need to consume fewer calories than you burn throughout the day, thereby forcing your body to burn stored fats instead.

Now that you've calculated your EER, you know what your baseline is. But how many calories should you subtract from that to encourage weight loss?

Traditional wisdom states that 3500 calories are about one pound of fat. By that logic, cutting out 500 calories from your EER per day should equal one pound of weight loss per week.

how many calories should i eat to lose weight with exercise

Of course, some factors can affect the result, such as how you're taking in those calories and how active your metabolism is, but the fundamental principle holds true for most people who need to lose weight.

In a 2008 study by National Institute of Health, researcher Kevin Hall found that the heavier you weigh, the more the 500-calorie deficit is going to affect your weight loss. This means that if you have a lot of weight to lose, then losing 500 calories should work great for you. But if you're relatively close to your healthy weight, then you may need to adjust your daily deficit a little higher to see results.

Calorie Consumption for Weight Gain

Your calorie consumption adjustment for weight gain is a little more complicated because the reason you need to gain weight will affect how many calories you need to add to your EER.


If you are attempting to gain weight due to being underweight, then your process will be the exact opposite of losing weight. The fact that 3500 calories are equal to one pound of fat still applies. You just need to add 500 calories to your weekly intake rather than subtracting it.

Like losing weight, your starting weight and other health issues may affect how effective this process is, so adjust the additional calories as needed.

how many calories should i eat to gain weight

Muscle Mass

If you want to gain weight to increase muscle mass, then it is also recommended to start off with a 500-calorie increase per day. However, in this case, it is especially important to focus on the quality of those calories. Try to make sure you're eating them in the form of fruits, vegetables, and healthy proteins. 

How Many Calories Should You Eat a Day? Medical Conditions and Calorie Consumption

Some medical conditions affect your body's ability to burn calories. Other conditions might affect the body's insulin, which can then cause calories that are consumed in the form of carbohydrates to be processed differently than others.

Hypothyroidism is one of the most common causes of weight gain or weight loss stagnation, especially in women. Conversely, this condition can make gaining weight a real challenge for some people.

Other medical conditions that might affect how many calories you need to consume include Cushing's syndrome, Grave's and Hashimoto's disease, and low testosterone levels. If you suspect you may be suffering from one of these conditions, then work with your doctor to create a treatment that includes an ideal diet plan to achieve the results you want.

Determining how many calories should you eat a day is a science, but figuring out how the discussed formulas can work for you and your lifestyle can also be a bit of an art. With a little trial and error, you can find the best number of calories for you to achieve your health goals.

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