BMR Calculator
Calculate your Basal Metabolic Rate with scientific precision using three validated formulas: Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle. Discover how many calories your body burns at rest and get personalized TDEE values for every activity level.
Mifflin-St Jeor is the most accurate for most people (±10% accuracy).
How to Use the BMR Calculator
Choose Your Unit System
Select metric (kg, cm) or imperial (lbs, inches). The calculator automatically converts between systems for accurate calculations across all formulas.
Select BMR Formula
Choose from three scientifically validated formulas: Mifflin-St Jeor (most accurate for general population), Harris-Benedict (classic formula), or Katch-McArdle (best if you know body fat %).
Enter Your Information
Input gender, age, weight, and height. For Katch-McArdle, you'll need body fat percentage instead of gender/age/height. Be accurate - small errors can affect results by 50-100 calories.
Calculate BMR
Click 'Calculate BMR' to get your basal metabolic rate. Results show calories burned at rest and TDEE breakdowns for all activity levels.
Review TDEE by Activity Level
Check TDEE values for your actual activity level: sedentary (desk job), light (1-3 days exercise), moderate (3-5 days), active (6-7 days), or very active (intense daily training).
Set Calorie Targets
Use TDEE to set goals: subtract 500 cal for weight loss (0.5 kg/week), eat at TDEE to maintain, or add 500 cal for weight gain. Track for 2-3 weeks and adjust as needed.
BMR Formula Comparison
Mifflin-St Jeor
Most accurate for general population (±10%). Developed in 1990, it's the current gold standard recommended by dietitians.
Women: 10×weight + 6.25×height - 5×age - 161
Harris-Benedict
Classic formula from 1919, revised in 1984. Tends to overestimate by 5-10% but widely used and still reliable.
Women: 447.6 + 9.25×weight + 3.1×height - 4.33×age
Katch-McArdle
Most accurate if body fat % known. Gender-neutral formula based on lean body mass rather than total weight.
LBM = weight × (1 - body fat %)
Understanding BMR & TDEE
BMR Components
Your BMR covers: brain function (20%), heart/circulation (20%), kidneys (10%), liver (10%), breathing (10%), and other organs (30%). Muscle tissue burns more than fat even at rest.
Activity Multipliers
Sedentary: 1.2× (desk job), Light: 1.375× (1-3 days exercise), Moderate: 1.55× (3-5 days), Active: 1.725× (6-7 days), Very Active: 1.9× (athlete/physical job).
Metabolic Adaptation
During weight loss, BMR can drop 10-15% beyond what's expected from reduced body weight. This "adaptive thermogenesis" is why weight loss plateaus occur.
Thermic Effect of Food
Digesting food burns calories: protein (20-30%), carbs (5-10%), fat (0-3%). This is already included in TDEE calculations and adds 10% to daily burn on average.
Frequently Asked Questions
What is BMR (Basal Metabolic Rate)?▼
BMR is the number of calories your body burns at complete rest to maintain essential physiological functions like breathing, blood circulation, cell production, and nutrient processing. It represents 60-75% of your total daily calorie expenditure and is the minimum energy required to keep your body alive.
What's the difference between BMR and TDEE?▼
BMR is calories burned at rest only. TDEE (Total Daily Energy Expenditure) is your complete daily calorie burn including BMR plus all physical activity. TDEE = BMR × Activity Multiplier. For example, if your BMR is 1,500 and you're moderately active, your TDEE would be 1,500 × 1.55 = 2,325 calories.
Which BMR formula is most accurate?▼
Mifflin-St Jeor is considered the most accurate for the general population with ±10% accuracy. Harris-Benedict (revised) is the classic formula but tends to overestimate slightly. Katch-McArdle is most accurate if you know your body fat percentage, as it's based on lean body mass rather than total weight.
How do I measure my body fat percentage?▼
Common methods include: DEXA scan (most accurate), hydrostatic weighing, bioelectrical impedance scales (least accurate but accessible), skinfold calipers, and visual estimation using comparison photos. For the Katch-McArdle formula, accuracy matters - a 5% error in body fat can affect BMR by 100-150 calories.
Why is my BMR different from my friend's?▼
BMR varies based on age, gender, weight, height, muscle mass, genetics, and hormones. Men typically have 5-10% higher BMR than women due to more muscle mass. BMR decreases by 1-2% per decade after age 20. More muscle mass = higher BMR because muscle burns more calories than fat even at rest.
Can I increase my BMR?▼
Yes! Build muscle through strength training (muscle burns 3x more calories than fat). Stay active (regular exercise boosts metabolic rate). Eat enough protein (thermic effect of food). Avoid extreme calorie restriction (can lower BMR by 10-15%). Get adequate sleep and manage stress (affects hormones that regulate metabolism).
Should I eat below my BMR to lose weight?▼
No, eating below BMR is not recommended. Your BMR is the minimum your body needs for basic functions. Eating below it can slow metabolism, cause muscle loss, hormonal imbalances, and nutrient deficiencies. For weight loss, aim for 500 calories below TDEE (not BMR), which is still well above BMR for most people.
How accurate are online BMR calculators?▼
BMR calculators have ±10% accuracy for most people. They use population averages and can't account for individual factors like genetics, hormones, or metabolic conditions. Use the result as a starting point, track your actual weight changes over 2-3 weeks, then adjust calorie intake by ±200-300 calories as needed.
Does BMR change with weight loss?▼
Yes, BMR decreases as you lose weight because there's less body mass to maintain. For every 10 kg lost, BMR drops by approximately 100-150 calories. This is why weight loss slows over time. Recalculate your BMR every 5-10 kg lost and adjust calorie targets accordingly.
What affects BMR besides age and weight?▼
Muscle mass (higher = higher BMR), genetics (can vary 20-30% between individuals), hormones (thyroid, testosterone, cortisol), body temperature (fever increases BMR), medications, caffeine and stimulants (temporary boost), and environmental temperature (cold increases BMR slightly). Medical conditions like hypothyroidism can significantly lower BMR.