Calculate your Basal Metabolic Rate (BMR) - the number of calories your body burns at rest. Use the Mifflin-St Jeor or Harris-Benedict formula for accurate results.
Basal Metabolic Rate (BMR) is the minimum number of calories your body needs to perform essential functions while at complete rest. This includes breathing, blood circulation, cell production, nutrient processing, and maintaining body temperature.
BMR typically accounts for 60-75% of your total daily calorie expenditure and varies based on age, gender, weight, height, and body composition. Understanding your BMR is crucial for creating effective nutrition and weight management plans.
Developed in 2005, the Mifflin-St Jeor equation is considered the most accurate formula for calculating BMR for most people, with about 90% accuracy compared to laboratory metabolic testing. It is recommended by nutritionists and dietitians worldwide.
Men:
BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) + 5
Women:
BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) - 161
The Harris-Benedict equation is an older but still widely used method to calculate BMR. While less accurate than Mifflin-St Jeor for modern populations, it remains a reliable estimation tool.
Men:
BMR = 66 + (13.7 × weight in kg) + (5 × height in cm) - (6.8 × age)
Women:
BMR = 655 + (9.6 × weight in kg) + (1.8 × height in cm) - (4.7 × age)
Your BMR represents the calories you burn at complete rest. To determine your Total Daily Energy Expenditure (TDEE), multiply your BMR by an activity factor:
To lose weight, consume fewer calories than your TDEE (BMR × activity factor). A deficit of 500-750 calories per day typically results in 1-1.5 pounds of weight loss per week. Never eat below your BMR for extended periods, as this can slow metabolism and cause muscle loss.
To maintain your current weight, consume calories equal to your TDEE. This ensures you're providing enough energy for both your basal metabolic needs and daily activities.
To gain weight (muscle mass), consume more calories than your TDEE. A surplus of 250-500 calories per day, combined with strength training, typically results in healthy weight gain of 0.5-1 pound per week.
BMR decreases by approximately 2% per decade after age 20 due to loss of muscle mass and hormonal changes.
Men typically have higher BMR than women due to greater muscle mass and lower body fat percentage.
Muscle tissue burns more calories at rest than fat tissue. Higher muscle mass means higher BMR.
Some people naturally have faster or slower metabolisms due to genetic factors.
Thyroid hormones, cortisol, and other hormones significantly impact metabolic rate.
Extreme temperatures can increase BMR as the body works harder to maintain core temperature.
BMR calculators provide estimates based on population averages. Individual metabolic rates can vary by 10-15% from calculated values due to factors like genetics, hormones, and body composition.
For the most accurate measurement of your metabolic rate, consider professional testing such as indirect calorimetry, which measures oxygen consumption and carbon dioxide production. These tests are available at many fitness centers, hospitals, and research facilities.