top of page

Harris-Benedict Equation and Calorie Requirements

bowl of vegan food

Harris-Benedict Equation and Basal Metabolic Rate

The Harris-Benedict equation is a widely used formula. It estimates an individual's basal metabolic rate (BMR). This equation predicts the energy to maintain their body weight while at rest. It is in calories. It considers many factors, such as age, gender, and weight. It is key to understanding metabolic rate and daily energy use. How many calories should you eat a day? The Harris-Benedict equation can help you calculate your calorie intake needs.

Contributions of Benedict FG and Harris JA

Benedict FG and Harris JA developed the Harris-Benedict equation. It helps to calculate daily calorie needs. Their work shows how age, body composition, and moderate exercise (like sports 3-5 days a week) affect how many calories we burn. This research helps people understand how metabolism changes with age. It also shows how to adjust food intake accordingly.

What is the Average Calorie Intake?

The average calorie intake falls between the estimated ranges in the table below. The table considers various activity levels. Please remember they are approximations only, and you should listen to your body's hunger and fullness cues. I use Renpho smart scales to help me track body fat and muscle mass. Renpho Bluetooth scales (Amazon affiliate)

Activity Levels

  • Sedentary (little to no exercise)

  • Lightly active (light exercise, 1-3 days a week)

  • Moderately active (moderate exercise, 3-5 days a week)

  • Very active (hard exercise, 6-7 days a week)

  • Extra active (very hard exercise, and a physical job)

Plantz Matter table showing calorie intake

Daily Energy Expenditure and Exercise

To measure daily energy use accurately, you must consider not more than basal metabolic rate. You should also the level of activity. This includes daily exercise and other demanding activities that increase metabolic activity. By combining these, people can better picture of their total energy needs.

How Does Activity Level Impact my Calorie Intake and Health?

Sedentary applies to individuals who engage in little movement in their day. These people may work desk jobs or have mobility issues. Their day includes a lot of sitting or lying down with limited to no exercise.

Sedentary people are at greater risk of developing health issues, including cardiovascular disease, obesity, and metabolic disorders. Cardiovascular disease, including stroke, is the world's number one killer. If you fall into this category, look for ways to increase your daily movement. Start slowly and build up to avoid being overwhelmed or becoming injured.

Light activity is exercise or physical activity that is for a limited duration or irregular. People in this category may get some of their movement from daily tasks or inconsistent formal exercise with a low intensity or limited duration.

Some examples of light activity:

  • Household chores

  • Easy or brisk walking

  • Light jogging

  • Low-intensity recreational sports: golfing, easy swimming

  • Light weightlifting or gym workouts

Moderately active people regularly engage in moderate-intensity physical activity.

Examples of moderate activities include:

  • Power walking

  • Jogging or running

  • Cycling (indoor or outdoor)

  • Aerobic classes (classes with continuous movement)

  • Swimming laps

  • Team sports

  • Moderate weightlifting or resistance training

Strenuous exercise (very and extra active) involves high-intensity levels. It requires great effort and is challenging both physically and mentally. Hard exercise varies based on an individual's fitness level, but common characteristics are elevated heart rate, increased or heavy breathing and muscle fatigue.

Examples of hard exercise may include:

  • Running or sprinting

  • Fast cycling

  • High-intensity interval training (HIIT)

  • Weightlifting (powerlifting or high repetitions)

  • Competitive sports

Aerobic activities, like running or swimming, and anaerobic activities, such as weightlifting, need different energy. The Harris-Benedict equation calculator can help estimate calorie needs better. It does this by including these varying levels of demanding activities in its calculations.

Physical movement or exercise can provide many benefits, including improved cardiovascular health, increased strength and muscle tone, enhanced endurance, weight management, improved mood, and reduced stress.

Ensure you ease into exercise if you need to get used to it and learn the correct form. See a healthcare professional or a certified fitness trainer before starting any exercise program to increase your safety and avoid injury.

Managing health risks requires careful monitoring. This is especially true for conditions like diabetes mellitus. You have to track exercise and daily calories. The formula helps tailor diets and exercise to cut risks and promote health. Considering the energy used in both aerobic and anaerobic activities helps people meet their health goals.

Lean Body Mass and Energy Requirements

Lean body mass is crucial for metabolism. It is the largest part of the body that burns calories. You can adjust the Harris-Benedict equation to account for the lean body mass. This gives a more accurate estimate of the daily energy needs. This is especially helpful for athletes and those with low fat percentage.

Weight Management and the Harris-Benedict Formula

For those focused on weight loss, it is vital to understand their basal metabolic rate. They can do this through the Harris-Benedict formula. You can plan your diet and activity to create a calorie deficit. You just need to know how many calories your body needs to function. This approach can lead to effective weight management. It combines monitoring your weight in and your daily activity level.

How Do I Calculate My Daily Calorie Needs?

How much energy you should eat daily depends on key factors such as age, gender, hormonal profile, height, health conditions, medication, body composition, muscle mass, current weight, activity level, and weight management goals (loss, maintenance, or gain).

The Harris-Benedict Equation (HBE) is often used to estimate how many calories an individual requires. HBE is a formula used to approximate your basal metabolic rate (BMR), which gives you an approximation of the number of calories needed to maintain your bodily functions.

Functions such as breathing, circulation of blood, body temperature regulation and supporting organ function, while you are at rest. Calculating your BMR using HBE can give you a baseline for your calorie needs. However, it needs to be repeated that these numbers are only rough estimates.

If you are happy to work with approximations, it may be worth using this information when starting out on a weight management plan. I always advocate speaking to professionals before making dietary or lifestyle changes. Consult with a knowledgeable healthcare professional or a registered dietitian for a more accurate assessment based on your circumstances.

If you are a healthy individual without specific dietary needs and are eating a whole food plant-based diet, there is little need for calorie counting. Most people on this diet eat until satisfied and fill up on low-calorie density foods, so only a rough mental record is kept.

To work out your HBE, click here, this calculator has metric and imperial measures. A simple search for HBE will also do, as there are many free online tools to help you figure out your HBE.

HBE Formula for Women in the Metric System:

BMR = 655 + (9.6 x weight in kilograms) + (1.8 x height in centimetres) - (4.7 x age in years)

HBE Formula for Women in the Imperial System:

BMR = 655 + (4.35 x weight in pounds) + (4.7 x height in inches) - (4.7 x age in years)

HBE Formula for Men in the Metric System:

BMR = 66 + (13.75 x weight in kilograms) + (5 x height in centimetres) - (6.75 x age in years)

HBE Formula for Men in the Imperial System:

BMR = 66 + (6.23 x weight in pounds) + (12.7 x height in inches) - (6.8 x age in years)

Once you calculate your BMR, you can multiply it by an activity factor to estimate your total daily calorie needs:

  • Sedentary: BMR x 1.2

  • Lightly active: BMR x 1.375

  • Moderately active: BMR x 1.55

  • Very active: BMR x 1.725

  • Extra active: BMR x 1.9

Predictive Equations and Daily Calorie Needs

Predictive equations, like the Harris-Benedict formula, are useful mathematical formulas. It can help us estimate daily calorie expenditure. These equations account for factors such as age, gender, and lean body mass. They give a rough estimate of the body's basic energy needs. It can help tailor daily caloric intake to individual needs. This is useful for those managing their health goals. It works for maintaining, losing, or gaining weight.

Body Composition and Metabolic Activity

Differences in body composition matter. They are about the ratio of muscle to fat. These differences influence metabolism. Muscle is the largest body part that burns calories. Fat percentage plays a key role in health risks. This includes cardiometabolic diseases. The Harris-Benedict equation can reflect these differences with modifications. It provides personalized energy levels for diverse groups.

Body Cell Mass and Obesity in Adults

Body cell mass (BCM) is the part of your body made up of cells that are alive and working hard, like those in your muscles and organs. It's important because it shows how much of your body is active and using energy.

Doctors look at BCM to figure out if someone is healthy, or if they might be undernourished or sick. They use special tests, such as scans, to measure how much active cell mass you have. This helps them understand how well your body is functioning and how much energy you're using.

Body cell mass is important for figuring out how many calories obese adults need. The Harris-Benedict equation can be adjusted to account for the amount of muscle and fat in the body, giving a more precise calorie count. This helps create diet plans for obese people. It considers their higher risk for heart disease and other health issues.

Chronic Diseases and Calorie Needs

Chronic diseases like heart disease and diabetes affect how many calories your body needs. The Harris-Benedict equation helps estimate these needs. It does this by considering how illness lowers a person's energy. By including moderate exercise and looking at body fat, this method helps make health plans that better manage these diseases.


Everyone needs a different number of calories per day to function optimally and meet their weight management goals. Establishing a base number may be helpful but it is only an approximation.

Calorie density can be a helpful tool in weight management to read up on this topic read the blog What is Calorie Density? More importantly than the number of calories we eat is the quality of the foods we choose to put into your bodies.

Thank you for reading. If you found this helpful, please share.


bottom of page