BMR Calculator

Do you want to lose weight or gain weight? If so, you must know your basal metabolic rate (BMR). BMR is the energy our body needs to carry out basic functions while at rest. This energy is necessary for functioning vital organs, such as the heart, lungs, and brain.

BMR varies from person to person depending on various factors such as age, gender, body composition, genetics, and hormones.

Understanding and calculating your BMR are the most important factors in determining how many calories you need to eat each day to lose fat and gain weight.

The BMR calculator is easy to use and accurate. Once you know your BMR, you can use it to make a calorie deficit or a calorie surplus to reach your weight goals.

What Is Basal Metabolic Rate (BMR)

BMR (Basal Metabolic Rate) is the amount of energy (measured in calories) that the body needs to perform vital functions while at rest. In other words, it’s the energy your body needs to perform vital processes like breathing, circulating blood, regulating body temperature, and supporting the functions of vital organs such as the heart, brain, and kidneys.

The higher your BMR, the more calories you burn at rest. This means you can eat more calories daily and still lose weight.

There are many factors that can affect your BMR, including:

• Age: Your BMR decreases as you age.
• Sex: Men typically have higher BMRs than women.
• Body composition: People with more muscle mass have higher BMRs than people with more fat mass.
• Activity level: Your BMR increases when you are active.
• Genetics: Your BMR is partly determined by your genes.

Most people’s normal daily activity requirement is about 70% of total energy (calories) each day. Physical activity accounts for nearly 20% of expenditure, while digestion accounts for about 10%.

Your BMR can help you determine how many calories you need to consume each day to maintain your weight, lose weight, or gain weight.

• If you want to lose weight, you need to create a calorie deficit. This means eating fewer calories than your BMR. You can do this by eating a healthy diet and exercising regularly.
• If you want to gain weight, you need to create a calorie surplus. This means eating more calories than your BMR. You can do this by eating a calorie-dense diet and lifting weights.

Functions of Basal Metabolic Rate 

The BMR accounts for approximately 60-70 percent of the calories we burn or expend. This includes the energy that the body expends to maintain the functions of our body, such as:

• Heartbeat
• Cell production
• Respiration
• Maintenance of body temperature
• Blood circulation
• Nutrient processing

How Does BMR Affect Weight Loss And Weight Gain?

Weight Loss

To lose weight, you must consume fewer calories than you burn daily. To determine the calorie deficit required for weight loss, subtract 500-1000 calories from your BMR.

When you consume fewer calories than your BMR, you create a caloric deficit. This deficit forces your body to tap into its stored energy reserves, primarily in the form of fat, to meet its energy needs. A sustained caloric deficit leads to weight loss over time.

For example: if your BMR is 1500 calories per day and you consistently consume only 1200 calories per day. You are creating a 300-calorie deficit.

Weight Gain

You need to consume more calories than you burn daily to gain weight. Add 500-1000 calories to your BMR to determine the calorie surplus required.

This surplus provides the extra energy needed to support muscle growth and weight gain.

For example: if your BMR is 1800 calories per day and you consistently consume 2200 calories per day. You are creating a 400-calorie surplus.

The greater the difference between your calorie intake and your BMR, the faster the rate of weight change. However, it’s recommended to aim for a sustainable deficit or surplus of 500-1000 calories for healthy, manageable weight loss or gain over time.

How To Calculate BMR

The basic formula for calculating BMR (Basal Metabolic Rate):

The Harris-Benedict Equation was one of the earliest equations introduced. It was revised in 1984 to be more accurate and used until 1990 when the Mifflin-St Jeor Equation was introduced.

The Mifflin-St Jeor Equation is more accurate than the revised Harris-Benedict Equation.

Mifflin-St Jeor Equation To Calculate BMR:

• For men: BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) + 5

• For women: BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) – 161

Calories Required As Per Activity Level

The number of calories a person needs daily depends on how much physical activity they engage in. Those who are more active typically require more calories to fuel their bodies.

• Sedentary (little or no exercise): BMR x 1.2
• Lightly active (1-3 days of exercise per week): BMR x 1.375
• Moderately active (3-5 days of exercise per week): BMR x 1.55
• Very active (6-7 days of exercise per week): BMR x 1.725
• Extra active (very intense exercise or physical job): BMR x 1.9

Exercises Level

• Exercise: 15-30 minutes of elevated heart rate activity.
• Intense exercise: 45-120 minutes of elevated heart rate activity.
• Very intense exercise: 2+ hours of elevated heart rate activity.

Importance of Understanding BMR

Understanding your BMR can be important for several reasons, including:

1. Weight Management

Your BMR is the number of calories your body needs to maintain vital functions at rest.

It is important to know your BMR to determine how many calories you need to consume daily to lose, maintain or gain weight.

2. Tailored nutrition and exercise plans

If you know how many calories your body needs when you’re not working. You can adjust how much you eat each day and how much you exercise.

It helps you create a customized nutrition and exercise plan that suits your specific needs.

3. Understanding your body

Knowing your BMR can help you understand how your body works and how it responds to changes in your lifestyle, like changes in diet, exercise, and sleep.

Factors that Affect BMR

Several factors can affect BMR, including:

1. Age

BMR decreases with age, typically by about 1-2% per decade after age 20.

2. Gender

Men generally have a higher BMR than women because they have more muscle mass and less body fat.

3. Height

Infants and children have higher energy demands per unit of body weight due to the extra energy required to maintain the body temperature during the growth phase.

4. Weight

The higher the weight, the higher the BMR.

5. Body composition

Muscle tissue is more metabolically active than fat tissue, so a higher percentage of muscle mass typically has a higher BMR.

6. Genetics

Some people have a higher BMR due to genetics, while others have a lower BMR.

7. Hormones

Hormones play a role in regulating BMR. Thyroid hormones, for example, play a vital role in regulating metabolism.

8. Environmental factors

BMR can be influenced by factors such as temperature, altitude, and pollution.

For example, the body may have to work harder to maintain its internal temperature in cold weather, resulting in a higher BMR.

How To Use BMR To Lose Weight

BMR (Basal Metabolic Rate) plays an important role in weight loss. When we lose weight, we often lose both fat and muscle mass.

This can lower our BMR, as muscle tissue is more metabolically active than fat tissue. Therefore, a lower BMR means we burn fewer calories at rest, making it more challenging to maintain weight loss.

To counteract this effect, it is important to maintain or increase muscle mass through regular strength training and consume adequate protein to support muscle growth and maintenance.

Drastically reducing calorie intake can also lower BMR, as the body goes into “starvation mode” and conserves energy.

It is recommended to lose weight slowly by 1–2 pounds per week through a combination of diet and exercise to keep a healthy BMR.

A moderate calorie deficit of 500-750 calories per day can help achieve this goal without significantly impacting BMR.

Best Ways To Increase BMR To Lose Weight

• Build and maintain muscle mass: Muscle tissue is more metabolically active than fat tissue, which burns more calories at rest. Strength training exercises can help you build more muscle and increase your BMR.
• Engage in aerobic exercise: Aerobic exercise, such as running, cycling, or swimming, can also improve BMR. This is because it increases heart rate and increases metabolism.
• Eat a balanced diet: Eating a balanced diet that is rich in whole, nutrient-dense foods can also help increase BMR. This is because the body requires energy to digest and absorb nutrients.
• Drink plenty of water: Drinking water can increase BMR by supporting the body’s metabolic processes, including digestion and thermogenesis (the body’s heat production process).
• Get enough sleep: Sleep is essential in regulating hormones that affect metabolism, such as cortisol and insulin. Getting adequate sleep can help improve BMR and metabolic health.
• Manage stress: Chronic stress can lead to hormonal imbalances that can negatively impact BMR. Practicing stress-management techniques, such as meditation or yoga.

How To Use BMR To Gain Weight

When we consume more calories than our body requires for energy, the excess calories are stored as fat.

However, as we gain weight, our BMR also increases because the body requires more energy to maintain a larger body size.

To gain weight healthily while maintaining a healthy BMR, it is important to consume a calorie surplus of around 500-750 calories per day.

It is important to focus on consuming nutrient-dense foods rather than high-calorie, low-nutrient foods to support overall health..

In addition to consuming a calorie surplus, engaging in strength training exercises can help build muscle mass and increase BMR.

Consuming adequate protein is also crucial for muscle growth and maintenance.

How To Calculate Your BMR

Several formulas can be used to calculate BMR (Basal Metabolic Rate).

1. Mifflin-St. Jeor equations
2. Harris-Benedict equation
3. Katch-McArdle equation
4. Cunningham equation
5. Owen equation

1. Mifflin-St. Jeor equation

Our calculator tool above uses the Mifflin-St Jeor equation, which is thought to be the most accurate estimate.

• For men: BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) + 5

• For women: BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) – 161

Mifflin-St. Jeor Equation Example To Estimate BMR:

Let’s say a 40-year-old female weighs 70 kilograms (154 pounds) and is 170 centimeters (5 feet 7 inches) tall.

To calculate her estimated BMR using the Mifflin-St. Jeor equation, we need to use the following formula:

• BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) – 161

Substituting the values into the equation to get BMR:

• = (10 x 70) + (6.25 x 170) – (5 x 40) – 161
• = 700 + 1062.5 – 200 – 161
• = 1,401.5 calories per day

Therefore, this individual’s estimated BMR using the Mifflin-St. Jeor equation is 1,401.5 calories per day.

2. Harris-Benedict Revised Equation

The original Harris–Benedict equations were published in 1918 and 1919.^[1]

• Men BMR = 66.473 + ( 13.7516 × weight in kg ) + ( 5.0033 × height in cm ) – ( 6.755 × age in years )
• Woman BMR = 655.0955 + ( 9.5634 × weight in kg ) + ( 1.8496 × height in cm ) – ( 4.6756 × age in years )

Many experts consider the revised Harris-Benedict equation to be the accurate BMR calculation for most types of people.

The Harris–Benedict equations were revised by Roza and Shizgal in 1984.^[2]

• For men: BMR = 88.36 + (13.4 x weight in kg) + (4.8 x height in cm) – (5.7 x age in years)

• For women: BMR = 447.6 + (9.2 x weight in kg) + (3.1 x height in cm) – (4.3 x age in years)

Harris-Benedict Equation Example To Estimate BMR:

Let’s say a 40-year-old female weighs 70 kilograms (154 pounds) and is 170 centimeters (5 feet 7 inches) tall.

To calculate her estimated BMR using the Harris-Benedict equation, we need to use the following formula:

• For women: BMR = 447.6 + (9.2 x weight in kg) + (3.1 x height in cm) – (4.3 x age in years)

Substituting the values into the equation to get BMR:

• = 447.6 + (9.2 x 70) + (3.1 x 170) – (4.3 x 40)
• = 447.6 + 644 + 527 – 172 BMR
• = 1,452.17 calories per day

The estimated BMR using the Harris-Benedict equation is 1,452.17 calories per day.

3. Katch-McArdle Equation

The Katch-McArdle equation used the same formula to estimate the BMR (Basal Metabolic Rate) for both males and females.

The equation considers a lean body mass, which is the body’s weight minus the weight of fat. The Katch-McArdle equation is:

• BMR = 370 + (21.6 x lean body mass in kg)

The Katch-McArdle equation is considered to be more accurate than the Harris-Benedict and Mifflin-St. Jeor equations because it considers body composition. However, the accuracy of the Katch-McArdle equation depends on the accuracy of the body fat measurement.

You need to have their body fat percentage to calculate lean body mass.

To measure lean body fat, you can use skinfold caliper measurements, bioelectrical impedance analysis, or dual-energy X-ray absorptiometry (DEXA).

Katch-McArdle Equation Example To Estimate BMR:

Let’s say a 35-year-old male weighs 80 kilograms (176 pounds) and has a body fat percentage of 20%.

To calculate his lean body mass, we need to multiply his weight by (100 – body fat percentage) as follows:

• Lean body mass = 80 kg x (100% – 20%) = 64 kg

Using the Katch-McArdle equation, we can calculate his estimated BMR as follows:

• = 370 + (21.6 x lean body mass in kg) BMR
• = 370 + (21.6 x 64) BMR
• = 370 + 1,382.4 BMR
• = 1,752.4 calories per day

The estimated BMR using the Katch-McArdle equation is 1,908 calories per day.

This means that his body would burn approximately 1,752.4 calories per day if he were at complete rest, without any physical activity or food intake.

4. Cunningham equation

The Cunningham equation is a formula used to estimate BMR (Basal Metabolic Rate) for individuals who know their body fat percentage.

The equation considers the lean body mass, which is the body weight minus the body fat.

The Cunningham equation is:

• BMR = 500 + (22 x lean body mass in kg)

Cunningham Equation Example To Estimate BMR:

Let’s say a 35-year-old male weighs 80 kilograms (176 pounds) and has a body fat percentage of 20%. To calculate his lean body mass, we need to multiply his weight by (100 – body fat percentage) as follows:

• Lean body mass = 80 kg x (100% – 20%) = 64 kg

Using the Cunningham equation, we can calculate his estimated BMR as follows:

• = 500 + (22 x lean body mass in kg) BMR
• = 500 + (22 × 64) BMR
• = 500 + 1,408 BMR
• = 1,908 calories per day

The estimated BMR using the Cunningham equation is 1,908 calories per day.

5. Owen Equation

The Owen equation is another method to estimate BMR that considers body surface area. Here is the formula:

• BMR (men) = 879 + 10.2 x weight (kg) + 6.25 x height (cm) – 5.4 x age (years)
• BMR (women) = 795 + 7.2 x weight (kg) + 4.7 x height (cm) – 4.7 x age (years)

Owen’s Equation Example To Estimate BMR:

Note that the Owen equation is less commonly used than the Harris-Benedict or Mifflin-St. Jeor equations.

Let’s say a 25-year-old female weighs 65 kilograms (143 pounds) and is 170 centimeters (5 feet 7 inches) tall.

• BMR = 795 + (7.2 x weight in kg) + (4.7 x height in cm) – (4.7 x age in years)

Substituting the values into the equation to get BMR:

• = 795 + (7.2 x 65) + (4.7 x 170) – (4.7 x 25)
• = 795 + 468 + 799 – 117.5
• = 1,944.5 calories per day

Therefore, this individual’s estimated BMR using the Owen equation is 1,944.5 calories per day. This means that her body would burn approximately 1,944.5 calories per day if she were at complete rest, without any physical activity or food intake.

BMR Calculations Keynote:

According to a 2005 meta-analysis study on BMR, despite controlling all factors of metabolic rate, there remains an unknown variance of 26% among individuals. This means that even an average person on a regular diet may have expected BMR values, but there are still unknown factors that precisely determine BMR.

As a result, all BMR calculations, even those conducted by specialists using the most accurate methods, will not be completely accurate in their measurements.

Since not all human bodily functions are fully understood, estimating total daily energy expenditure (TDEE) based on BMR calculations is just an estimate.

BMR can provide a foundation when pursuing health or fitness goals, but it offers little else. The calculated BMR and TDEE may yield unsatisfactory outcomes due to their rough estimates.

However, maintaining a daily journal of exercise, food consumption, and other factors can aid in tracking progress and identifying areas for enhancement.

FAQs

How do you estimate your BMR?  

BMR can be estimated by using the Mifflin-St Jeor or Harris-Benedict equation. The basal metabolic rate can be estimated using height, weight, and age.

Why do you want to know your BMR? 

Understanding your basal metabolic rate (BMR) is crucial whether you are trying to lose, maintain, or gain weight.

Your BMR determines how many calories you should consume to meet your daily energy needs.

For weight loss, consuming fewer calories than your BMR is essential. However, even if you are not trying to lose weight, knowing your BMR is important for optimal nutrition, fitness, and overall health.

Can BMR change over time?

Yes, BMR can change over time because of factors like age, weight loss or gain, and changes in muscle mass. With age, your BMR may decrease, and with weight loss, your BMR may also decrease due to muscle mass loss.

How can I increase my BMR?

You can increase your BMR by doing strength training, eating protein-rich foods, and staying hydrated.

In addition, high-intensity interval training (HIIT) and other forms of physical activity can also increase your BMR..

Does everyone have the same BMR?

No, BMR can vary depending on factors such as age, gender, weight, height, and body composition.

Men generally have a higher BMR than women due to having more muscle mass on average.

Can I lose weight by only eating below my BMR?

While consuming fewer calories than your BMR can lead to weight loss, it is not recommended to eat significantly below your BMR for extended periods of time.

This can lead to nutrient deficiencies and other health problems.

How long does it take to see changes in BMR?

Changes in BMR can occur over time with consistent exercise and nutrition habits. It may take several weeks or months to see significant changes in BMR.

Conclusion

BMR (Basal Metabolic Rate) is crucial for maintaining a healthy weight and metabolic health. Maintaining a healthy BMR is important for weight loss and weight gain.

To maintain a healthy BMR, engaging in regular physical activity, consuming a balanced and nutrient-dense diet, prioritizing getting enough sleep, and managing stress are important.

In addition, to increase BMR, it is important to build and maintain muscle mass through strength training exercises, engage in aerobic exercise, and consume adequate protein.

References:

1. Johnstone AM, Murison SD, Duncan JS, Rance KA, Speakman JR, Factors influencing variation in basal metabolic rate include fat-free mass, fat mass, age, and circulating thyroxine but not sex, circulating leptin, or triiodothyronine1. Am J Clin Nutr 2005; 82: 941-948.
2. Schwarz, N. A., Rigby, B. R., La Bounty, P., Shelmadine, B., & Bowden, R. G. (2011). A Review of Weight Control Strategies and Their Effects on the Regulation of Hormonal Balance. Journal of Nutrition and Metabolism, 2011.
3. Buchholz, A. C., Rafii, M., & Pencharz, P. B. (2001). Is resting metabolic rate different between men and women? British Journal of Nutrition, 86(6), 641–646.
4. Lazzer, S., Bedogni, G., Lafortuna, C. L., Marazzi, N., Busti, C., Galli, R., De Col, A., Agosti, F., & Sartorio, A. (2010). Relationship between basal metabolic rate, gender, age, and body composition in 8,780 white obese subjects. Obesity (Silver Spring), 18(1), 71-8. doi:10.1038/oby.2009.162

Manish Kumar

Manish is a NASM-certified fitness and nutrition coach with over 10 years of experience in weight lifting and fat loss fitness coaching. He specializes in gym-based training and has a lot of knowledge about exercise, lifting technique, biomechanics, and more.

Through “Fit Life Regime,” he generously shares the insights he’s gained over a decade in the field. His goal is to equip others with the knowledge to start their own fitness journey.