Basal Metabolic Rate (BMR) Calculator

Have you ever pondered how much energy your body requires just to sustain life?

The Basal Metabolic Rate (BMR) is a crucial concept in nutrition that elucidates the energy expended at rest, and factors such as age, gender, and physical activity influence this calorie requirement of your body. What’s more, even minor lifestyle adjustments can significantly impact your metabolism.

While there are multiple formulas to calculate it, the simplest approach is to use a calculator like the one you’ll find in this article.

BMR Calculator

What is the Basal Metabolic Rate (BMR)?

The BMR indicates the energy required for our body to perform basic functions at rest, that is, the minimal calories needed to keep us alive and functional without physical activity. BMR constitutes approximately 60-75% of the daily energy expenditure.

These basic functions include breathing, circulation, temperature regulation, cell growth and repair, along with brain and nervous system maintenance. The BMR varies among individuals due to factors such as age, gender, weight, height, body composition, and genetics.

What is the purpose of the BMR?

The Basal Metabolic Rate has multiple applications in the nutritional sphere, such as:

a) Determining daily caloric needs: The BMR is fundamental for estimating an individual’s required calories, considering their unique characteristics and physical activity. By knowing this, we can factor in the additional calories needed for daily activities and exercise.

b) Designing diets and weight loss plans: It aids in the planning of personalized diets and weight loss programs. To lose weight healthily, it’s crucial to create a caloric deficit, i.e., consuming fewer calories than you expend. The BMR sets the foundation for achieving such a deficit.

c) Monitoring metabolic health: It enables the evaluation of a person’s metabolic health. Extremely high or low values may indicate health issues that require medical attention. Significant changes in BMR can reflect variations in body composition, such as loss or gain of muscle mass.

d) Scientific research: It’s a common parameter in studies related to nutrition, physiology, and obesity. These investigations aim to understand the differences in this rate among populations, the factors affecting it, and how dietary or exercise interventions can influence BMR and total energy expenditure.

BMR in the calculation of maintenance calories

Basal metabolism is just one component of the total calories your body requires daily to maintain its weight and function properly. Maintenance calories correspond to the total amount of calories you need to consume to maintain your current weight, considering your BMR and the energy spent on daily activities and exercise.

To calculate your maintenance calories, you first need to know your BMR, which you can obtain with our calculator. Then, adjust this value according to your level of physical activity. For this, there are calorie calculators like this one.

Formulas for calculating BMR and maintenance calories

Various formulas are available for calculating BMR and maintenance calories, such as the Harris-Benedict equation and the Mifflin-St Jeor equation, which consider age, sex, weight, and height.

• Mifflin-St Jeor Equation: Males: BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) + 5 Females: BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) – 161

• Harris-Benedict Equation (original): Males: BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) – (5.677 x age in years) Females: BMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) – (4.330 x age in years)

To calculate maintenance calories, multiply BMR by an activity factor that reflects your level of physical activity:

• Sedentary (little or no exercise): BMR x 1.2
• Lightly active (light exercise or sports 1-3 days a week): BMR x 1.375
• Moderately active (moderate exercise or sports 3-5 days a week): BMR x 1.55
• Very active (intense exercise or sports 6-7 days a week): BMR x 1.725
• Extremely active (very intense exercise or daily physical work): BMR x 1.9

Please note that these formulas and activity factors are approximations and may not be precise for everyone. For more accurate information, consult a healthcare professional.

Can basal metabolic rate be modified?

While certain factors influencing BMR, such as age, genetics, and sex, cannot be modified, there are other variables that can be adjusted to impact our BMR.

Exercise: Regular physical activity, especially strength training, can increase muscle mass, which in turn can boost BMR. Muscle mass is metabolically more active than fat, which means it burns more calories even at rest.

Diet: Consuming a balanced and nutrient-rich diet, especially proteins, can contribute to an increase in BMR. Diet-induced thermogenesis is the process by which the body burns calories in digesting, absorbing, and processing food, with proteins demanding more energy in this process.

Sleep: Lack of sleep can negatively impact BMR. During sleep, the body carries out repairs and maintains vital functions. Adequate, high-quality sleep can enhance metabolic function and, therefore, BMR.

Hydration: Staying well-hydrated is vital for optimal metabolic function. Drinking sufficient water helps to maintain an appropriate balance of body fluids, enabling efficient metabolism.

Although it is possible to modify BMR to some extent, the changes are usually not overly significant. Maintaining a healthy lifestyle, including a balanced diet, regular physical activity, adequate hydration, and good sleep habits, can help to optimize metabolic function and improve overall health.

References

Relationship between basal metabolism and maintenance calories:

• Müller, M. J., Bosy-Westphal, A., & Kutzner, D. (2002). Metabolically active components of fat-free mass and resting energy expenditure in humans: recent lessons from imaging technologies. Obesity reviews, 3(2), 113-122.

Formulas for calculating BMR and maintenance calories:

• Mifflin, M. D., St Jeor, S. T., Hill, L. A., Scott, B. J., Daugherty, S. A., & Koh, Y. O. (1990). A new predictive equation for resting energy expenditure in healthy individuals. The American journal of clinical nutrition, 51(2), 241-247.
• Harris, J. A., & Benedict, F. G. (1918). A biometric study of human basal metabolism. Proceedings of the National Academy of Sciences of the United States of America, 4(12), 370.
• Frankenfield, D., Roth-Yousey, L., & Compher, C. (2005). Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association, 105(5), 775-789.

Activity factors for determining maintenance calories:

• Swain, D. P., & American College of Sports Medicine. (2014). ACSM’s resource manual for guidelines for exercise testing and prescription. Lippincott Williams & Wilkins.
• Ainsworth, B. E., Haskell, W. L., Herrmann, S. D., Meckes, N., Bassett Jr, D. R., Tudor-Locke, C., … & Leon, A. S. (2011). 2011 Compendium of Physical Activities: a second update of codes and MET values. Medicine & Science in Sports & Exercise, 43(8), 1575-1581.