Basal Metabolic Rate Calculator
Calculate how many calories your body burns at rest using the validated Harris-Benedict (1919) and Mifflin-St Jeor (1990) formulas.
Important Medical Disclaimer
This calculator is an educational and clinical decision support tool. Results DO NOT replace professional medical evaluation, laboratory tests, or clinical judgment. Always consult a qualified healthcare professional for diagnosis, treatment, and clinical decisions. Calculations are based on scientifically validated formulas but may not be applicable to all patients.
Calculate BMR
What is Basal Metabolic Rate (BMR)?
Basal Metabolic Rate (BMR) represents the minimum amount of energy (calories) your body needs to maintain vital functions at complete rest, such as breathing, blood circulation, cell production, and temperature regulation. BMR accounts for approximately 60-75% of total daily energy expenditure and is influenced by age, sex, weight, height, body composition, and genetic factors.
Calculation Formulas
Mifflin-St Jeor (1990) - Recommended
Considered more accurate and up-to-date. Developed in 1990 based on more recent studies and a more diverse population.
Harris-Benedict (1919) - Classic
Original formula created in 1919. Still widely used but may overestimate caloric expenditure in some populations.
How to Use the BMR Calculator
To calculate your BMR, enter your weight in kilograms, height in centimeters, age in years, and select your biological sex. Choose the desired formula (we recommend Mifflin-St Jeor for greater accuracy). The result will show how many calories your body burns per day at rest. To know your Total Daily Energy Expenditure (TDEE), see the automatically calculated values for each physical activity level. Use TDEE to plan your diet: consume this amount to maintain weight, less to lose weight (300-500 kcal deficit), or more to gain weight.
Important Limitations and Considerations
BMR is an estimate based on population averages. Individual factors such as muscle mass, genetics, hormones (thyroid, cortisol), ambient temperature, stress, dieting history, and health status can significantly affect actual metabolism. Athletes with high muscle mass tend to have higher BMR. People on prolonged restrictive diets may develop metabolic adaptation (reduced BMR). BMR naturally decreases with age (about 2-3% per decade after 30 years) due to muscle mass loss. Always consult a nutritionist for personalized guidance on your caloric needs.
Frequently Asked Questions about BMR
What's the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is caloric expenditure at complete rest, maintaining only vital functions. TDEE (Total Daily Energy Expenditure) is BMR multiplied by the physical activity factor, representing total daily expenditure including exercise and daily activities. For example, if your BMR is 1500 kcal and you're moderately active (factor 1.55), your TDEE will be 2325 kcal/day.
How can I increase my BMR?
The most effective way to increase BMR is to gain muscle mass through strength training (weightlifting), as muscles burn more calories at rest than fat. Other strategies include: eating regular meals (avoiding prolonged fasting), sleeping adequately (7-9 hours), avoiding very restrictive diets that cause metabolic adaptation, staying hydrated, and consuming sufficient protein. Aerobic exercise also helps temporarily.
Why does BMR decrease with age?
With aging, there is a natural loss of muscle mass (sarcopenia) and reduction in hormonal activity (mainly growth hormone and sex hormones), which decreases basal metabolism. After age 30, BMR decreases about 2-3% per decade. Regular strength training helps minimize this reduction by maintaining muscle mass.
Is BMR different for men and women?
Yes, significantly. Men generally have 5-10% higher BMR because they tend to have more muscle mass and lower body fat percentage than women. Hormones also play a role: testosterone (higher in men) increases metabolism. The formulas account for these biological differences in calculations, which is why there are separate equations for each sex.
Can I safely use BMR to lose weight?
Yes, but with caution. To lose weight healthily, consume calories below your TDEE (not BMR!), but never less than your own BMR. Consuming below BMR for prolonged periods can cause metabolic adaptation, muscle mass loss, and nutritional deficiencies. A moderate deficit of 300-500 kcal/day from TDEE is recommended for gradual and sustainable loss of 0.5-1 kg per week. Always consult a nutritionist.
Scientific References
- 1. Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247.
- 2. Harris JA, Benedict FG. A Biometric Study of Human Basal Metabolism. Proc Natl Acad Sci U S A. 1918;4(12):370-373.
- 3. FAO/WHO/UNU. Human energy requirements. Report of a Joint FAO/WHO/UNU Expert Consultation. Rome: Food and Agriculture Organization, 2004.