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Calculate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using the revised Harris-Benedict equation, one of the most widely recognized metabolic formulas.
The Harris-Benedict equation is a formula used to estimate an individual's basal metabolic rate (BMR) based on their weight, height, age, and biological sex. The equation was first published in 1918 and revised in 1984 for improved accuracy.
To calculate TDEE (Total Daily Energy Expenditure), multiply your BMR by your activity factor:
Scientists J. Arthur Harris and Francis G. Benedict published their groundbreaking equation after studying the metabolism of 239 subjects. Their research was conducted at the Carnegie Institute of Washington's Nutrition Laboratory in Boston. The original equation was derived from indirect calorimetry measurements.
Roza and Shizgal published a revised version of the Harris-Benedict equation using modern data. The revision improved accuracy by accounting for changes in population characteristics over the 66 years since the original study. This is the version most commonly used today and the one implemented in this calculator.
The Harris-Benedict equation revolutionized our understanding of human metabolism and energy expenditure. It provided the first scientifically validated method to estimate caloric needs, which has been invaluable in clinical nutrition, weight management, and sports performance. While newer equations exist (like Mifflin-St Jeor), Harris-Benedict remains one of the most recognized and widely used metabolic formulas in the world.
BMR is the number of calories your body burns at complete rest to maintain vital functions like breathing, circulation, cell production, and temperature regulation.
TDEE is the total number of calories you burn in a day, including BMR plus all physical activity, exercise, and the thermic effect of food (calories burned digesting food).
The Harris-Benedict equation estimates your Basal Metabolic Rate (BMR) - the calories you burn at rest - and your Total Daily Energy Expenditure (TDEE) when combined with an activity factor. It's used for nutrition planning, weight management, and understanding caloric needs.
For most people, it's accurate within ±10-20%. However, it can overestimate calories for obese individuals and doesn't account for body composition. The Mifflin-St Jeor equation (1990) is slightly more accurate for modern populations.
The original equation was published in 1918. The revised version (1984) by Roza and Shizgal updated the coefficients using modern data, improving accuracy. This calculator uses the revised 1984 version, which is more appropriate for current populations.
Both are valid. Mifflin-St Jeor (1990) is considered slightly more accurate for modern populations and is preferred by many dietitians. However, Harris-Benedict is still widely used and has historical significance. The difference is usually only 5-10%.
Men typically have more muscle mass and less body fat than women of the same weight, leading to higher BMR. The different formulas account for these biological differences in body composition and hormones.
It's not recommended long-term. Consistently eating below BMR can slow metabolism, cause muscle loss, hormonal issues, and make future weight loss harder. A moderate deficit (10-25% below TDEE) is safer and more sustainable.
Recalculate every 10-15 pounds of weight change, when you change activity levels significantly, or every 3-6 months. BMR decreases as you lose weight and age, so periodic recalculation ensures accuracy.
Formulas provide estimates. Individual variations in genetics, NEAT (non-exercise activity), metabolic efficiency, and past dieting history can cause 10-20% differences. Track your weight for 2-4 weeks to find your true TDEE.
This calculator provides estimates for educational purposes only. Individual calorie needs vary based on genetics, body composition, medical conditions, medications, and other factors. The Harris-Benedict equation may not be accurate for athletes, obese individuals, or those with metabolic conditions. Consult with a registered dietitian or healthcare provider for personalized nutrition guidance.