BMR Calculator
Calculate your Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation (primary) and Harris-Benedict equation (secondary). BMR represents the minimum calories your body needs at complete rest.
How This Calculator Works
Formula: Mifflin-St Jeor (Primary) and Harris-Benedict (Secondary)
The Mifflin-St Jeor equation (1990) is the primary formula: for men, BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 5; for women, BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161. The revised Harris-Benedict equation (1984) is provided as a secondary reference: for men, BMR = 13.397 x weight(kg) + 4.799 x height(cm) - 5.677 x age + 88.362; for women, BMR = 9.247 x weight(kg) + 3.098 x height(cm) - 4.330 x age + 447.593.
Limitations
- BMR formulas are population-based estimates and may not reflect individual metabolic variations.
- These equations do not account for lean body mass, which significantly affects metabolic rate.
- Accuracy is reduced for very muscular individuals, the elderly, and those with metabolic conditions.
- Actual BMR can only be precisely measured through indirect calorimetry in a clinical setting.
These calculations are estimates based on established formulas. Individual results vary. Consult a healthcare professional before making significant changes to your diet or exercise routine.
Basal Metabolic Rate (BMR) is the number of calories your body requires to perform its most basic life-sustaining functions while at complete rest. These functions include breathing, blood circulation, cell production, nutrient processing, and temperature regulation. BMR typically accounts for 60-75% of your total daily calorie expenditure.
This calculator provides results from two established equations. The Mifflin-St Jeor equation, published in 1990, is recommended by the Academy of Nutrition and Dietetics as the most reliable predictive equation for estimating BMR. The original Harris-Benedict equation (1919, revised 1984) is included as a secondary reference, as it was the standard for decades and remains widely cited.
Several factors influence your BMR. Body size plays a major role — larger bodies require more energy to maintain. Lean muscle mass is more metabolically active than fat tissue, so body composition significantly affects BMR. Age causes a gradual decline in BMR, primarily due to loss of muscle mass. Sex also plays a role, as males typically have higher BMR due to greater lean mass on average.
Understanding your BMR is the first step toward calculating your total daily energy needs. By itself, BMR tells you the minimum calories your body needs at rest. To determine your actual daily needs, your BMR must be multiplied by an activity factor to account for movement and exercise. This produces your Total Daily Energy Expenditure (TDEE).
You should never consume fewer calories than your BMR for extended periods without medical supervision. Eating below your BMR can lead to nutrient deficiencies, muscle loss, metabolic adaptation, and other health concerns.