What is a BMR Calculator?
The Basal Metabolic Rate (BMR) Calculator estimates the amount of energy expended while at rest in a neutrally temperate environment, and in a post-absorptive state (meaning that the digestive system is inactive, which requires about 12 hours of fasting). BMR represents the minimum amount of energy needed to keep your body functioning, including breathing, circulation, cell production, nutrient processing, protein synthesis, and ion transport.
How Does Our BMR Calculator Work?
Our calculator offers three scientifically-validated formulas:
- Mifflin-St Jeor Formula (Recommended): The most accurate for general population, developed in 1990.
- Harris-Benedict Formula (Revised): The classic formula, revised in 1984 for better accuracy.
- Katch-McArdle Formula: Best for lean individuals with known body fat percentage.
BMR Formulas
Mifflin-St Jeor Formula
For Men: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age(years) + 5
For Women: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age(years) - 161
Harris-Benedict Formula (Revised)
For Men: BMR = 88.362 + (13.397 × weight(kg)) + (4.799 × height(cm)) - (5.677 × age(years))
For Women: BMR = 447.593 + (9.247 × weight(kg)) + (3.098 × height(cm)) - (4.330 × age(years))
Katch-McArdle Formula
For Both: BMR = 370 + (21.6 × lean body mass(kg))
Where: Lean Body Mass = weight(kg) × (1 - body fat percentage/100)
Activity Level Multipliers
To calculate daily calorie needs, BMR is multiplied by activity factors:
- Sedentary (1.2): Little or no exercise
- Light Activity (1.375): Light exercise 1-3 times per week
- Moderate Activity (1.55): Moderate exercise 4-5 times per week
- High Activity (1.725): Hard exercise 6-7 times per week
- Very High Activity (1.9): Very hard exercise, physical job, or training twice a day
Factors Affecting BMR
- Body Size: Larger bodies have higher BMR
- Body Composition: Muscle tissue burns more calories than fat tissue
- Gender: Men typically have higher BMR than women
- Age: BMR generally decreases with age
- Genetics: Some people naturally have faster or slower metabolism
- Climate: Extreme temperatures can affect BMR
- Hormones: Thyroid hormones significantly impact BMR
Using BMR for Weight Management
- Weight Loss: Create a caloric deficit by eating fewer calories than your total daily energy expenditure
- Weight Maintenance: Match your caloric intake to your total daily energy expenditure
- Weight Gain: Create a caloric surplus by eating more calories than your total daily energy expenditure
Tips to Boost Your Metabolism
- Build muscle through strength training
- Stay hydrated and drink cold water
- Eat protein-rich foods
- Get adequate sleep (7-9 hours)
- Include high-intensity interval training (HIIT)
- Don't skip meals or drastically restrict calories
- Drink green tea or coffee
- Manage stress levels
Important Disclaimer
BMR calculations provide estimates based on mathematical formulas and may not reflect individual variations. Factors such as genetics, hormones, medications, and health conditions can significantly affect actual metabolic rate. This tool should not replace professional medical advice. Consult with a healthcare provider or registered dietitian for personalized nutrition and weight management guidance.