Metabolism Analysis

Advanced BMR Calculator

Understand your daily caloric needs with a comprehensive metabolic rate calculator based on leading scientific formulas.

What is BMR?

Basal Metabolic Rate (BMR) is the number of calories your body needs to maintain basic physiological functions while at complete rest. This includes breathing, blood circulation, temperature regulation, cell growth, and brain function.

Your BMR constitutes approximately 60-75% of your total daily caloric expenditure, with the remainder coming from physical activity and food digestion (thermic effect of food).

Why Calculate BMR?

Establish baseline caloric needs for weight management
Design effective nutrition plans for specific goals
Understand metabolic efficiency and energy distribution
Track changes in metabolism over time

Gender

Age (years)

years

Weight (kg)

Height (cm)

Activity Level

Sedentary Lightly active Moderately active Very active Extremely active

Lightly active: Exercise or light physical activity 1-3 days/week (walking, light gardening)

Your Metabolic Results

Basal Metabolic Rate (BMR)

1,640 calories/day

Calories needed to maintain basic bodily functions at complete rest

Total Daily Energy Expenditure (TDEE)

2,255 calories/day

Total calories needed based on your activity level

2,255

BMR

1,640 (73%)

Activity

378 (17%)

Food Digestion

237 (10%)

Calorie Targets by Goal

Weight Loss

Moderate (0.5kg/week) 1,755

Aggressive (1kg/week) 1,255

Not recommended to go below your BMR for extended periods

Maintenance

2,255 calories

To maintain current weight with your activity level

Weight Gain

Moderate (0.25kg/week) 2,505

Bulking (0.5kg/week) 2,755

For muscle gain, combine with appropriate resistance training

Personalized Analysis

Based on your profile, your metabolic rate is in the normal range for your age and gender. Your daily caloric expenditure is primarily determined by your BMR (73%), with physical activity contributing 17% and food digestion accounting for 10%.

To optimize your metabolism, focus on regular strength training to build and maintain muscle mass, as muscle tissue burns more calories at rest than fat tissue. Regular physical activity, staying hydrated, and eating sufficient protein can also support a healthy metabolic rate.

Metabolic Rate Calculation Methods

Mifflin-St Jeor Equation

Considered the most accurate for the general population, this equation was published in 1990 and has become the gold standard for estimating BMR.

For men:

BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5

For women:

BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161

Source: The American Journal of Clinical Nutrition, 1990

Harris-Benedict Equation

Originally published in 1919 and revised in 1984, this was the standard for many years. It tends to slightly overestimate BMR in most populations.

For men:

BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) - (5.677 × age in years)

For women:

BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) - (4.330 × age in years)

Source: Journal of the American Dietetic Association, 1984

Katch-McArdle Formula

This formula factors in lean body mass (LBM), making it more accurate for athletic individuals with higher muscle mass and lower body fat percentages.

For both men and women:

BMR = 370 + (21.6 × Lean Body Mass in kg)

Where:

LBM = Weight in kg × (1 - Body Fat % / 100)

Source: Medicine & Science in Sports & Exercise, 1994

WHO/FAO/UNU Equations

Developed by the World Health Organization, these equations use different calculations for different age ranges, making them more precise across the lifespan.

Age-specific equations using weight in kg:

Men (18-30): BMR = 15.3 × weight + 679

Men (31-60): BMR = 11.6 × weight + 879

Women (18-30): BMR = 14.7 × weight + 496

Women (31-60): BMR = 8.7 × weight + 829

Source: WHO Technical Report Series, 2001

Factors Affecting Metabolic Rate

Primary Factors

Body Composition
Muscle tissue requires more energy to maintain than fat tissue. Higher muscle mass means higher BMR.
Age
BMR decreases approximately 1-2% per decade after age 20, primarily due to loss of muscle mass.
Sex Hormones
Testosterone promotes muscle growth and higher BMR, while estrogen can influence fat distribution and metabolism.
Genetics
Family history can influence metabolic rate by up to 10%, affecting how efficiently you burn calories.

Secondary Factors

Dietary Habits
Thermic effect of food (TEF) varies: protein (20-30%), carbs (5-10%), fats (0-3%). Extreme caloric restriction can lower BMR.
Physical Activity
Exercise increases TDEE immediately and can elevate BMR for up to 48 hours. Regular resistance training builds muscle for long-term BMR boost.
Health Status
Conditions like hyperthyroidism can increase BMR, while hypothyroidism can decrease it. Illness and fever can temporarily raise BMR.
Environmental Factors
Cold environments can increase BMR through thermogenesis. Stress hormones like cortisol can impact metabolism and fat storage.

Research & References

Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. "A new predictive equation for resting energy expenditure in healthy individuals." American Journal of Clinical Nutrition, 1990. Link
Frankenfield D, Roth-Yousey L, Compher C. "Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review." Journal of the American Dietetic Association, 2005. Link
Cunningham JJ. "A reanalysis of the factors influencing basal metabolic rate in normal adults." American Journal of Clinical Nutrition, 1980. Link
World Health Organization. "Energy and protein requirements: Report of a Joint FAO/WHO/UNU Expert Consultation." WHO Technical Report Series, 2001. Link
Müller MJ, Bosy-Westphal A, Later W, Haas V, Heller M. "Functional body composition: insights into the regulation of energy metabolism and some clinical applications." European Journal of Clinical Nutrition, 2009. Link
Schofield WN. "Predicting basal metabolic rate, new standards and review of previous work." Human Nutrition: Clinical Nutrition, 1985. Link
Speakman JR, Selman C. "Physical activity and resting metabolic rate." Proceedings of the Nutrition Society, 2003. Link