What is Basal Metabolic Rate (BMR)?
Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain essential physiological functions like breathing, circulation, cell production, and nutrient processing. It represents the minimum energy your body needs to stay alive.
BMR vs RMR vs TDEE
- BMR (Basal Metabolic Rate): Calories burned at absolute rest with zero movement
- RMR (Resting Metabolic Rate): Similar to BMR but measured with minimal movement; typically 10-20% higher than BMR
- TDEE (Total Daily Energy Expenditure): Your total calorie burn including BMR plus all daily activities and exercise
Mifflin-St Jeor vs Harris-Benedict Formula
Our calculator offers both popular BMR formulas:
- Mifflin-St Jeor (Recommended): Developed in 1990, this formula is more accurate for modern populations and is considered the gold standard by most nutritionists and researchers. It accounts for changes in lifestyle and body composition since the early 1900s.
- Harris-Benedict: Created in 1918 and revised in 1984, this older formula tends to overestimate calorie needs by 5-15% for sedentary individuals but can be useful for very active populations.
How to Use Your BMR for Weight Goals
Once you know your BMR and TDEE, you can adjust your calorie intake:
- Weight Loss: Create a deficit of 500-1000 calories below TDEE for 1-2 lbs/week loss
- Weight Maintenance: Match your calorie intake to your TDEE
- Weight Gain: Create a surplus of 250-500 calories above TDEE for gradual muscle gain
Factors That Affect Your BMR
- Age: BMR decreases by about 2% per decade after age 20
- Sex: Men typically have 5-10% higher BMR due to more muscle mass
- Body Composition: Muscle tissue burns more calories than fat tissue
- Height & Weight: Larger bodies require more energy
- Genetics: Some people naturally have faster or slower metabolisms
- Hormones: Thyroid function significantly impacts metabolic rate
Activity Level Multipliers
To calculate TDEE, your BMR is multiplied by an activity factor:
- Sedentary (1.2x): Desk job, little to no exercise
- Lightly Active (1.375x): Light exercise 1-3 days/week
- Moderately Active (1.55x): Moderate exercise 3-5 days/week
- Very Active (1.725x): Hard exercise 6-7 days/week
- Extra Active (1.9x): Athlete or very physical job
💡 Pro Tips
- ✓ Reassess your BMR every 10-15 pounds of weight change
- ✓ Never eat below your BMR for extended periods
- ✓ Track your actual weight changes and adjust calories accordingly
- ✓ Most people overestimate their activity level - be honest!
- ✓ BMR calculators provide estimates; individual variation exists