Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest — the energy required just to keep your heart beating, lungs breathing, and cells functioning. It is measured under strict resting conditions: fasted, awake, and in a thermoneutral environment.
BMR accounts for approximately 60-75% of your Total Daily Energy Expenditure (TDEE). Understanding your BMR gives you the foundation for any nutrition or weight management strategy, since all other calorie estimates build on top of it.
BMR is not the same as TDEE. TDEE factors in how active you are — your BMR multiplied by an activity coefficient. If you want to know how many calories you need per day to lose, maintain, or gain weight, use our calorie calculator which applies the full activity-adjusted calculation.
The American Dietetic Association recommends the Mifflin-St Jeor equation as the most accurate formula for estimating BMR in healthy adults. Studies consistently show it outperforms older equations across diverse populations.
Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161The original Harris-Benedict equation was revised by Roza and Shizgal in 1984. While widely recognized and historically significant, research shows it tends to overestimate BMR by 5% in many populations compared to Mifflin-St Jeor.
Men: BMR = 88.362 + (13.397 × weight kg) + (4.799 × height cm) − (5.677 × age)
Women: BMR = 447.593 + (9.247 × weight kg) + (3.098 × height cm) − (4.330 × age)BMR decreases approximately 2% per decade after age 20, primarily due to loss of lean muscle mass. Resistance training is one of the most effective strategies to slow this decline and preserve metabolic rate as you age.
Males typically have a 5-10% higher BMR than females of the same height, weight, and age. This difference is largely explained by the greater proportion of lean muscle mass in males, which is metabolically more active than fat tissue.
Muscle tissue burns approximately 6 kcal per kilogram per day at rest, while fat tissue burns only about 2 kcal per kilogram per day. Two people at the same body weight can have meaningfully different BMRs depending on their muscle-to-fat ratio.
Genetic variation accounts for up to 40% of the difference in BMR between individuals. Thyroid hormone levels, mitochondrial efficiency, and inherited metabolic tendencies all contribute to why two people with identical body compositions can have noticeably different calorie needs.
Short or poor sleep can lower your resting energy use slightly and changes the hormones that control hunger, leptin and ghrelin. Long-term stress raises cortisol, which is linked to more fat around the abdomen.
Your BMR is the starting point, not the endpoint. To estimate your total daily calorie needs, multiply your BMR by an activity factor: sedentary (×1.2), lightly active (×1.375), moderately active (×1.55), very active (×1.725), or extremely active (×1.9). The result is your TDEE — the number of calories required to maintain your current weight.
Never eat below your BMR for extended periods. Doing so puts your body in a severe deficit that forces it to break down muscle tissue for fuel, which lowers your BMR further and creates a cycle that makes long-term weight management harder. Safe deficits are typically 300-500 kcal below TDEE, not below BMR.
Ready to go further? Use our calorie calculator to calculate your activity-adjusted TDEE and set a goal-specific calorie target. Or start a free Bennu trial to track your food intake with a coach supporting your progress.
BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest — just to keep you alive. It includes breathing, circulation, cell production, and temperature regulation. Knowing your BMR helps you understand the minimum energy your body needs, which is the starting point for any calorie or weight management plan.
BMR is your resting calorie burn — no movement, no digestion, just survival. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor that accounts for exercise, daily movement, and the thermic effect of food. TDEE is what you actually need to eat to maintain weight; BMR is a lower bound you should rarely go below.
The Mifflin-St Jeor equation (1990) is considered the most accurate for modern populations by the American Dietetic Association. The revised Harris-Benedict equation (1984) is a reasonable alternative but tends to overestimate by 5-15%, especially in overweight individuals. This calculator shows both so you can compare.
First, multiply your BMR by an activity factor to get your TDEE. Then eat below your TDEE (not below your BMR) to create a calorie deficit. A moderate deficit of 300-500 calories below TDEE produces steady fat loss of roughly 0.3-0.5 kg per week without excessive hunger or muscle loss.
Exercise doesn't directly change your BMR during the workout — that's accounted for in TDEE via the activity multiplier. However, resistance training increases muscle mass over time, and muscle is more metabolically active than fat, so consistent strength training can raise your BMR by 50-100+ calories per day over months.
Two people with the same height and weight can have different BMRs due to body composition (muscle vs fat ratio), genetics (which can account for up to 40% of variation), hormonal differences, and lifestyle factors like sleep quality and stress levels. Formula-based estimates use population averages and can't capture individual variation.
Yes — BMR decreases roughly 1-2% per decade after age 20, primarily because of gradual loss of lean muscle mass. This is why many people gain weight in their 30s and 40s without changing their diet. Resistance training is the most effective way to slow this decline by preserving and building muscle.
Not for extended periods without medical supervision. Your BMR represents the minimum energy your body needs for basic survival functions. Eating below it for weeks can trigger metabolic adaptation (your body slows down), muscle loss, hormonal disruption, and nutrient deficiencies. Always base your calorie deficit on TDEE, not BMR.
Formula-based BMR estimates are typically within 10% of measured values for most people. The gold standard is indirect calorimetry (measuring oxygen consumption), but that requires lab equipment. For practical purposes, use the Mifflin-St Jeor result as a starting point and adjust based on real-world tracking over 2-4 weeks.
Recalculate every time your weight changes by 2-3 kg (4-6 lb), or roughly every 4-6 weeks during active weight loss or gain. BMR changes with your body weight and composition — a target that worked at 90 kg won't be accurate at 80 kg.
This calculator provides estimates for educational purposes only. It is not medical advice. Consult a registered dietitian or physician before making significant dietary changes, especially if you have medical conditions, are pregnant, or have a history of eating disorders.
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