Find out exactly how many calories your body burns at rest. Your Basal Metabolic Rate (BMR) is the foundation of any nutrition plan — from weight loss to muscle building.
Basal Metabolic Rate (BMR) is the energy your body needs at complete rest to maintain vital functions — breathing, circulation, cell repair, and temperature regulation — expressed in kilocalories per day. The Mifflin–St Jeor equation (1990) is widely used: for men, BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5; for women, the constant is −161 instead of +5. BMR typically accounts for 60–75% of total daily energy expenditure. It rises with greater lean mass and falls with age. BMR is a planning baseline for calorie targets, not a prescription; actual needs vary with genetics, thyroid function, and daily activity beyond rest. Activity level is applied separately when estimating total daily energy needs. Individual variation from thyroid function, genetics, and lean mass can shift true resting needs. Use BMR as a structured starting point for nutrition planning rather than a rigid prescription.
Worked example: A 30-year-old man weighing 80 kg and 180 cm tall: BMR = (10 × 80) + (6.25 × 180) − (5 × 30) + 5 = 800 + 1,125 − 150 + 5 = 1,780 kcal/day at rest.
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Your metabolic baseline drives every nutrition decision.
Never eat below your BMR for extended periods. Your body burns these calories just to survive — cutting below this triggers muscle breakdown, hormonal disruption, and metabolic adaptation that makes future fat loss harder.
Your Total Daily Energy Expenditure (TDEE = BMR × activity multiplier) is the number that actually matters for weight management. Eat 300–500 kcal below your TDEE to lose fat. Eat above it to build muscle.
Each kg of muscle burns approximately 13 kcal/day at rest. Adding 5 kg of muscle raises your BMR by ~65 kcal/day — making it easier to maintain a healthy weight long-term without constant calorie restriction.
BMR tells you the floor of daily energy use before purposeful exercise or occupational movement. Most people need well above BMR once walking, work, and training are included — that total is TDEE. Use BMR to sanity-check extreme diets: eating far below BMR for long periods can impair recovery and lean mass unless medically supervised.
BMR and metabolism explained.
BMR is the calories burned at complete rest. TDEE (Total Daily Energy Expenditure) multiplies BMR by your activity level to estimate total daily calorie burn. TDEE is the number you use for weight management decisions.
It is accurate within ±10% for most adults. It tends to slightly overestimate BMR for very obese individuals and underestimate for very muscular people. Re-calculate as your weight changes.
Yes. Resistance training builds muscle, which raises resting metabolic rate. Adequate protein intake preserves muscle during caloric deficit. High-intensity interval training (HIIT) also elevates post-exercise oxygen consumption (EPOC), temporarily raising metabolic rate for hours after exercise.
The primary cause is sarcopenia — the gradual loss of muscle mass that begins around age 30 (0.5–1% per year). Since muscle is metabolically active, less muscle means lower BMR. Resistance training can largely prevent and even reverse this decline.
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Browse All Tools →Resting energy estimates use the Mifflin–St Jeor equations, a common clinical and research baseline:
This calculator gives a general estimate for education and planning. It is not a medical diagnosis and does not replace advice from a qualified healthcare professional. Talk to your doctor before acting on these results — especially if you are pregnant, under 18, or managing an existing medical condition.