Calculate your Basal Metabolic Rate using the revised Harris-Benedict equation (1984). Estimate daily calorie needs at rest for weight management and nutrition planning.
The Harris-Benedict BMR Calculator estimates your Basal Metabolic Rate — the number of calories your body burns at complete rest to maintain vital functions like breathing, circulation, cell production, and temperature regulation. Originally published in 1918 by James Arthur Harris and Francis Gano Benedict, this equation is one of the most recognized metabolic formulas in nutrition science and clinical medicine.
This calculator uses the revised Harris-Benedict equation (Roza & Shizgal, 1984), which improved the accuracy of the original formula using a larger and more diverse dataset. The revised equation remains widely used in clinical nutrition, dietetics, and fitness programming, though the Mifflin-St Jeor equation (1990) is now considered slightly more accurate for the general population.
BMR represents the minimum energy your body needs to function. It typically accounts for 60-75% of total daily energy expenditure. Understanding your BMR is the foundation for calculating your Total Daily Energy Expenditure (TDEE) and setting caloric targets for weight loss, weight gain, or maintenance. This calculator also provides estimated TDEE values at different activity levels for practical meal planning.
Knowing your BMR is essential for evidence-based nutrition planning. Whether you want to lose fat, build muscle, or maintain your current weight, your BMR is the starting point for calculating how many calories you need each day. The Harris-Benedict equation is particularly well-established in clinical settings and has decades of validation behind it. By applying an activity multiplier, you can estimate your total daily calorie needs with reasonable accuracy.
Revised Harris-Benedict (Roza & Shizgal, 1984): Males: BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) − (5.677 × age in years). Females: BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) − (4.330 × age in years). TDEE = BMR × Activity Factor: Sedentary (1.2), Lightly Active (1.375), Moderately Active (1.55), Very Active (1.725), Extra Active (1.9).
Result: BMR ≈ 1,826 kcal/day
BMR = 88.362 + (13.397 × 80) + (4.799 × 178) − (5.677 × 35) = 88.362 + 1071.76 + 854.222 − 198.695 = 1,815.6 kcal/day. At moderate activity (×1.55), the estimated TDEE would be approximately 2,814 kcal/day. This means the individual burns about 1,816 calories just at rest and approximately 2,814 calories with regular moderate exercise.
The original Harris-Benedict equation was published in 1918 based on indirect calorimetry measurements of 239 subjects. It was one of the first widely adopted formulas for estimating basal metabolism and became the standard reference in clinical nutrition for decades. In 1984, Roza and Shizgal published a revision using data from 337 subjects, updating the coefficients to improve accuracy. This revised version is the equation used in modern clinical practice.
Several BMR prediction equations exist, each with strengths and limitations. The Harris-Benedict equation (revised 1984) is well-validated and widely recognized. The Mifflin-St Jeor equation (1990) is considered slightly more accurate for the general population and is recommended by the American Dietetic Association. The Katch-McArdle equation uses lean body mass and is preferred for athletic or very lean individuals. The Cunningham equation is similar to Katch-McArdle but with higher coefficients, making it suitable for athletes.
Beyond age, sex, height, and weight, several factors influence BMR. Genetics account for an estimated 40-80% of BMR variation between individuals of the same size. Thyroid hormones directly regulate metabolic rate — hypothyroidism can reduce BMR by 15-30%. Ambient temperature affects BMR through thermogenesis. Pregnancy increases BMR progressively. Certain medications, caffeine, and nicotine can temporarily elevate metabolic rate. Chronic illness and nutritional status also play significant roles.
BMR is the foundation of evidence-based nutrition planning. To estimate daily calorie needs, multiply BMR by an appropriate activity factor to get TDEE. For fat loss, create a moderate deficit (10-20% below TDEE). For muscle gain, add a surplus (10-15% above TDEE). For maintenance, eat at TDEE. Track your weight and adjust every 2-4 weeks based on actual results, as prediction equations provide starting estimates that need individualization through monitoring.
BMR is the number of calories your body burns at complete rest to maintain essential physiological functions — heart beating, lungs breathing, brain functioning, cells dividing, and body temperature regulation. It is measured under strict conditions: after 12 hours of fasting, 8 hours of sleep, in a thermally neutral environment, and at complete physical rest. BMR typically accounts for 60-75% of total daily calorie expenditure.
The revised Harris-Benedict equation (1984) is accurate to within ±10-15% for most individuals when compared to indirect calorimetry (the gold standard). It tends to overestimate BMR in obese individuals and may underestimate in very lean or muscular individuals. The Mifflin-St Jeor equation is generally considered slightly more accurate for the general population, but Harris-Benedict remains widely used and validated.
BMR (Basal Metabolic Rate) is measured under strict laboratory conditions after prolonged fasting and rest. Resting Metabolic Rate (RMR) is measured under less strict conditions and is typically 10-20% higher than BMR. In practice, the terms are often used interchangeably, and most prediction equations actually estimate something closer to RMR than true BMR.
First, estimate your TDEE by multiplying BMR by your activity factor. To lose weight, create a moderate caloric deficit of 300-500 calories below TDEE. A 500-calorie daily deficit produces approximately 0.45 kg (1 lb) of fat loss per week. Never eat below your BMR for extended periods, as this can cause metabolic adaptation, muscle loss, and nutritional deficiencies.
BMR decreases with age primarily due to progressive loss of metabolically active lean tissue (muscle) and changes in hormonal balance (declining growth hormone, testosterone, and thyroid function). After age 30, adults typically lose 3-8% of muscle mass per decade without intervention. Regular resistance training and adequate protein intake can significantly slow this decline.
Males and females have fundamentally different body compositions due to hormonal differences. Males typically have more lean mass and less body fat, resulting in higher BMR at the same height and weight. The Harris-Benedict equation accounts for this with different coefficients and constants for each sex, improving prediction accuracy compared to a single unisex equation.
Yes. The most effective way to increase BMR is to build lean muscle mass through resistance training, since muscle tissue burns more calories at rest than fat tissue. Other factors that can modestly increase BMR include: adequate protein intake (thermic effect of food), avoiding prolonged caloric restriction, maintaining thyroid health, getting sufficient sleep, and staying physically active throughout the day.
Sedentary (1.2): desk job with little or no exercise. Lightly Active (1.375): light exercise 1-3 days per week. Moderately Active (1.55): moderate exercise 3-5 days per week. Very Active (1.725): hard exercise 6-7 days per week. Extra Active (1.9): very hard exercise, physical job, or training twice daily. Choose the level that best describes your typical week.