BMR Calculator
Calculate your Basal Metabolic Rate—the calories burned simply staying alive at resting state.
Parameters & Inputs
Summary & Breakdown
Daily Burn by Activity Level
About the BMR Calculator
Your Basal Metabolic Rate (BMR) represents the caloric energy demanded by your internal organs€”including cardiac circulation, brain activity, respiratory diaphragm movement, hepatic filtration, and cellular sodium-potassium pumps€”while at rest in a thermally neutral environment.
BMR accounts for approximately 60% to 75% of your total daily energy expenditure. Knowing this resting number prevents you from setting dangerously severe caloric deficits that trigger metabolic compensation and lethargy.
This calculator compares the modern Mifflin-St Jeor standard against the historical revised Harris-Benedict formula, establishing your physiological floor.
How the Calculations Work
Calculates resting energy expenditure via the Mifflin-St Jeor formula: BMR = (10 * weight in kg) + (6.25 * height in cm) - (5 * age) + sex constant (+5 male, -161 female).
BMR = 10*W + 6.25*H - 5*A + s
Variables & Definitions
- W: Body mass in kilograms (kg)
- H: Stature height in centimeters (cm)
- A: Chronological age in years
- s: +5 for biological males, -161 for biological females
A 30-year-old male weighing 75 kg at 175 cm tall has: BMR = (10*75) + (6.25*175) - (5*30) + 5 = 750 + 1093.75 - 150 + 5 = 1,698.75 (rounds to 1,699 kcal/day).
Key Terms Explained
Thermic Effect of Food (TEF)
The energy expended digesting, absorbing, and storing nutrients (~10% of total daily burn).
Metabolic Adaptation
The physiological down-regulation of resting thyroid and energy expenditure in response to prolonged caloric deficits.
Mifflin-St Jeor Equation
The modern clinical equation established in 1990 found to be within 10% of indirect calorimetry in healthy adults.
Resting Metabolic Rate (RMR)
Slightly higher than BMR (up to 10%), measured under less rigorous fasting and sleep conditions.
Practical Tips & Pitfalls to Avoid
Never eat below your BMR without clinical supervision
Consuming fewer calories than your resting organs require causes fatigue, hair loss, and muscle wasting.
Build resistance training habits
Muscle tissue is metabolically active; gaining 3-5 kg of lean mass increases baseline daily calorie burn around the clock.
Recalculate BMR as you lose weight
A lighter body requires less energy to move and maintain, slightly lowering BMR over time.
Ensure adequate sleep
Chronic sleep deprivation disrupts hunger hormones leptin and ghrelin, interfering with metabolic recovery.
Frequently Asked Questions
BMR is what you burn staying completely motionless in bed all day. TDEE (Total Daily Energy Expenditure) adds all physical movement, work, and digestion.
Men generally possess a higher percentage of lean muscle mass and greater average stature, requiring more resting caloric energy.
No. While metabolic adaptation temporarily lowers energy expenditure during severe diets, metabolism recovers when calories and body weight normalize.
The thermic energy needed to warm ice water to body temperature burns only ~8 calories per cup€”a negligible physiological effect.
BMR declines slightly with age primarily due to natural age-related sarcopenia (loss of muscle tissue), which can be largely mitigated with strength training.