How Many Calories Should You Eat in a Day?

Medically Reviewed By William C. Lloyd III, MD, FACS
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Some diets today discourage counting calories, relying instead on having you calculate point values for certain foods. Others ask you to focus on eating (or not eating) certain types of foods, such as veggies or carbs. But knowing how many calories in a day you should eat—as well as how many you’re actually consuming—can be important information. This is true whether you’re trying to lose, gain or maintain weight, as well as stay healthy. So how can you figure out how many calories you need?

Average daily calorie needs

Calories are a measure of energy, and represent what you need to take in every day for your body to be properly fueled. The amount you need depends on your age, your gender, your height and weight, and your physical activity level. How many calories you burn also depends on your basal metabolic rate. This rate drops as you get older, which is why older people generally need fewer calories to stay the same weight.

Here are average daily calorie needs, according to the United States Office of Disease Prevention and Health Promotion:

  • Adult women: 1,600 to 2,400 calories
  • Adult men: 2,000 to 3,000 calories
  • Young children: 1,000 to 2,000 calories
  • Older children and adolescents: 1,400 to 3,200 calories (with boys generally at the higher end of the scale)  

 

How can you calculate your daily calories?

The calorie ranges listed above are very wide. To find a number closer to what you need, you can make use of various daily calorie calculators. With these, you fill in your sex, age, height and weight. You also estimate your activity level: sedentary, moderately active (includes walking 1.5 to 3 miles per day at 3 to 4 miles per hour), and active (walking more than 3 miles per day at 3 to 4 miles per hour).

Two online calorie counters will automatically assess how many calories you should ingest to either maintain or lose weight:

You can also figure your own daily calorie needs using these steps:

  • Calculate your weight in kilograms. If you’re like most Americans, you know your weight in pounds. To translate to kilograms, divide that number by 2.2.
  • Multiply the result by 30.

So, if you weigh 150 pounds, your weight in kilograms is about 68.19; multiplying this by 30 nets you a daily calorie count of 2046. If you are very active or very sedentary, you may need to add or subtract a few calories if you want to maintain your current weight.

Fitness experts at health clubs or gyms also may be able to figure your recommended daily calorie intake by measuring your oxygen consumption and carbon dioxide production.

How many calories do you need if you want to lose weight?

The old rule of thumb used to be that it takes about 3,500 calories to gain one pound of weight. Put another way, you need to cut 3,500 calories if you want to lose a pound. Under this thinking, if you cut 500 calories from your daily diet (either through diet or exercise, or a combination of both), you would lose one pound per week.

However, in recent years, researchers have found this to be an oversimplification of a complicated process. In 2013, scientists analyzed seven previous weight-loss studies where people's food intake was closely monitored, and found that instead of losing a pound for every 3,500 calories lost, people's weight loss amounts varied. Men tended to lose weight faster than women, and younger people lost faster than older people, with variations within those groups.

As people lost weight, it took longer to lose more weight. They hit plateaus where they had to cut more calories than 3,500 to lose a pound. The National Institutes of Health still recommends dieters try cutting 500 calories a day, but cautions not to expect a precise "calories-in, calories-out" equation. You may not lose that pound as easily as you might hope.

When is it dangerous to consume too few calories?

Also keep in mind that it's possible to eat too few calories. In general, say experts, going lower than 1,000 calories per day (especially without medical supervision) means you might not be getting enough nutrients to stay healthy.

Eating too few calories can cause various problems:

  • Deficiencies of cancer-fighting vitamins and other important nutrients such as calcium, which could result in osteoporosis or other conditions
  • Slow metabolism, which could cause you to feel sluggish and cold, and to become constipated
  • Slower thinking or “brain fog,” caused by not enough glucose getting to your brain
  • Gallstones, which can occur when you’re on a very low-calorie diet (800 daily calories or fewer)

If you have concerns about your optimal calorie level, it’s best to talk with your doctor or other health professional to help you calculate a number that’s safe and effective for meeting your weight and health goals.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 May 6
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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