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Every day, you burn calories when you move around, exercise, and go about your daily tasks.

Your body even burns calories at rest, through basic functions like:

  • breathing
  • circulating blood
  • cell processes

Ever wondered how many calories you burn each day? The Harris-Benedict formula can help you figure this out.

This formula calculates your basal metabolic rate (BMR), which is the number of calories your body needs to function at rest.

With one more calculation, you can work out how many calories you need each day to maintain your current weight. Eating fewer calories than this will result in weight loss.

It is important to note that while calorie intake and exercise are an important part of weight loss, hormones and metabolism also play a major role.

The Harris-Benedict formula, or Harris-Benedict equation, lets you work out how many calories you need to eat per day. The formula is adjusted based on your sex, age, and weight to give a personalized answer.

This equation was first published in 1918. Researchers then revisited the calculation in 1984 and again in 1990 to improve its accuracy.

Once you work out your BMR, you can multiply this figure by a measure of your daily activity level — ranging from sedentary to extra active — to find out the number of calories you need to consume each day to maintain your weight.

The next sections will tell you how to do these calculations. If you’re looking for a quick answer, you can get an online calculator to do the legwork for you.

Step 1. Calculate BMR

To calculate your BMR, use your sex, age, and weight to adjust the formula.

The original formulas for calculating this number are as follows, using pounds for weight, inches for height, and years for age.

For males, use the following equation:

  • 66 + (6.2 x weight) + (12.7 x height) – (6.76 x age) = BMR for males

For example, a 40-year-old, 180 pound, 6-foot-tall man has a BMR of 1,829.8. This means that, at rest, they’ll burn approximately 1,829.8 calories in a day (equation: 66 + (6.2 x 180) + (12.7 x 72) – (6.76 x 40) = 1,829.8).

For females, use the following equation:

  • 655.1 + (4.35 x weight) + (4.7 x height) – (4.7 x age) = BMR for females

For example, a 40-year-old, 150-pound, 5 foot 6-inch-tall woman has a BMR of 1,429.7 (equation: 655.1 + (4.35 x 150) + (4.7 x 66) – (4.7×40) = 1,429.7).

Step 2. Work out your activity level

From there, you must figure out your activity level. The activity levels the equation uses are as follows:

  • 1.2, or sedentary (little to no exercise)
  • 1.375, or lightly active (light exercise 1–3 days per week)
  • 1.55, or moderately active (moderate exercise 3–5 days per week)
  • 1.725, or very active (hard exercise 6–7 days per week)
  • 1.9, or extra active (very hard exercise, training, or a physical job)

For example, a postal worker who walks all day for their job would have an activity level of 1.725 depending on the length and difficulty of their route.

A desk worker who walks several times a week for exercise would have an activity level of 1.55.

Step 3. Use the full equation

Putting everything together, the Harris-Benedict equation is as follows:

  • BMR x activity level = calories needed to maintain weight

A 150-pound female who’s extra active will need 2,716 calories to maintain their weight (equation: 1,429.7 (BMR) x 1.9 (activity level) = 2,716 calories).

A 180-pound male who’s moderately active will need 2,836 calories to maintain their weight (equation: 1829.8 (BMR) x 1.55 (activity level) = 2,836 calories).

As you can see in the above examples, activity level has a lot to do with how many calories a person needs each day.

Many people think they need to exercise hard to burn calories throughout the day.

While exercise does burn a lot of calories, your body also burns calories while you’re doing normal daily tasks. How much you burn has to do with how much you weigh.

For example, people will burn the following number of calories in 30 minutes of doing these tasks based on their weight:

Task125-pound person155-pound person185-pound person
walking at 4.5 mph150186222
cleaning the gutters150186222
mowing the lawn135167200
gardening135167200
washing the car135167200
walking at 4 mph135167200
walking at 3.5 mph120149178
playing with the kids (moderate activity)120149178
grocery shopping (with cart)105130155
cooking7593111
sitting in meetings496072
light office work455667
computer work415161
standing in line384756
reading344250
watching television232833
sleeping192328

You can use an interactive online calculator to find out how many calories you’ll burn while doing different activities. To use it, simply input your activity, time spent doing it, and your weight.

Yes, males and females burn calories at different rates. This is why sex is included as a variable in the equation, along with age and weight, which also affect the number of calories a person burns.

Males generally have less body fat than females. They also tend to have more muscle mass. More muscle means the body burns a higher number of calories while at rest.

So, generally speaking, males usually burn more calories than females overall. That said, the individual’s body composition plays an important role.

Once you know how many calories your body needs to maintain your current weight, eating fewer calories than this will usually lead to weight loss.

Many people choose to reduce their calorie intake by 500 kcal per day to achieve weight loss.

For example, a person with a calorie need of 2,800 per day to maintain their current weight can lose weight if they eat 2,300 calories per day.

As an alternative, you can eat the same number of calories but do more exercise to burn calories. This will also lead to a calorie deficit.

A calorie deficit means that you’re eating fewer calories than you’re burning, which is the key to effective weight loss.

It is important to note that while calorie intake and exercise are an important part of weight loss, hormones and metabolism also play a major role.

Conventional wisdom is that you need to burn 3,500 calories to lose 1 pound. This means reducing calorie intake by 500 kcal per day to lose 1 pound in a week.

Researchers have since called the 3,500-calorie rule into question, because it’s not quite that simple. In reality, the number of calories you need to burn depends on how much body fat and muscle you have.

Read more about how many calories to eat for weight loss here.

Losing weight isn’t always as simple as plugging numbers into a calculator.

The most effective way to lose weight and keep it off in the long term, is to follow a balanced lifestyle that includes:

  • healthful foods
  • regular exercise
  • adequate quality sleep
  • effective ways to reduce stress

Some people also find these tips can help when they’re trying to lose weight:

  • reading labels to learn the nutritional facts about the foods you eat
  • keeping a food diary to see what you eat in a day and identify areas for improvement
  • choosing lower calorie options when choosing foods, such as skim milk instead of whole milk, air-popped popcorn instead of chips, and thin crust pizza instead of thick crust
  • reducing processed, high-calorie, low-nutrition foods, like candy, cookies, and chips
  • being mindful of portion sizes to avoid eating more than one portion by accident
  • putting food on a plate rather than eating it straight from the bag
  • using smaller plates and bowls
  • eating slowly and chewing food thoroughly
  • waiting at least 20 minutes before going back for seconds
  • making small, sustainable changes instead of favoring a crash diet

Shop for food diaries to help get you started.