BMR Calculator
Calculate your basal metabolic rate and daily calorie needs. Includes Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle formulas with TDEE calculations.
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Daily Expenditure
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📊 Daily Needs by Activity
💪 Weight Change Goals
🧮 BMR Calculation Formulas
Mifflin-St Jeor Equation (Most Accurate - 1990)
Considered the gold standard for BMR calculation. More accurate than Harris-Benedict for modern populations.
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
Example: 25-year-old male, 70 kg, 180 cm
BMR = 10(70) + 6.25(180) − 5(25) + 5
BMR = 700 + 1125 − 125 + 5 = 1705 kcal/day
Harris-Benedict Equation (Classic - 1919, Revised 1984)
The original and widely-used formula, though slightly less accurate than Mifflin-St Jeor.
BMR = 88.362 + (13.397 × Weight kg) + (4.799 × Height cm) − (5.677 × Age)
For Women (Revised):
BMR = 447.593 + (9.247 × Weight kg) + (3.098 × Height cm) − (4.330 × Age)
Katch-McArdle Formula (Body Composition Based - 1977)
Uses lean body mass instead of total weight. More accurate for people who know their body fat percentage.
Where: Lean Body Mass = Weight × (1 − Body Fat %)
Example: 70 kg with 20% body fat
LBM = 70 × (1 − 0.20) = 56 kg
RDEE = 370 + (21.6 × 56) = 370 + 1209.6 = 1579.6 kcal/day
TDEE Calculation
Convert BMR to daily calorie needs based on activity level.
Activity Factors:
• Sedentary (no exercise) = 1.2
• Lightly Active (1-3 days/week) = 1.375
• Moderately Active (3-5 days/week) = 1.55
• Very Active (6-7 days/week) = 1.725
• Extremely Active (2x daily) = 1.9
📊 TDEE & Calorie Guidelines
What is TDEE?
Total Daily Energy Expenditure (TDEE) is the total calories your body burns in a day. It includes: Basal Metabolic Rate (60-70% of TDEE), Thermic Effect of Food (10%), and Activity/Exercise (remaining percentage).
Using TDEE for Weight Goals
Weight Loss: Consume 500 calories below TDEE daily = lose ~0.5 kg/week. Weight Gain: Consume 500 calories above TDEE daily = gain ~0.5 kg/week. Maintenance: Eat at TDEE level.
Activity Level Definitions
| Activity Level | Factor | Description |
|---|---|---|
| Sedentary | 1.2 | Little or no exercise, desk job |
| Lightly Active | 1.375 | Exercise 1-3 days/week |
| Moderately Active | 1.55 | Exercise 3-5 days/week |
| Very Active | 1.725 | Intense exercise 6-7 days/week |
| Extremely Active | 1.9 | Very heavy exercise or physical labor job |
Exercise Definitions
Exercise: 15-30 minutes of elevated heart rate activity. Intense Exercise: 45-120 minutes of elevated heart rate activity. Very Intense Exercise: 2+ hours of elevated heart rate activity.
📐 Understanding BMR Formulas
Why Multiple Formulas?
Different formulas use different methodologies and were developed from different research populations. Mifflin-St Jeor used modern data from 1990. Harris-Benedict is the classic from 1919-1984. Katch-McArdle accounts for body composition. Results typically vary by 5-10%.
Which Formula to Use?
- General Use: Mifflin-St Jeor (most accurate for average person)
- Body Fat Known: Katch-McArdle (most accurate if you know body fat %)
- Reference: Harris-Benedict (classic formula, still widely used)
- Best Practice: Average multiple formulas for better estimate
Factors Affecting BMR
Increase BMR: Building muscle, regular exercise, adequate sleep, proper hydration, eating whole foods. Decrease BMR: Caloric restriction, aging (decreases ~2-8% per decade), sedentary lifestyle, certain medications.
BMR vs RMR
BMR (Basal Metabolic Rate): Measured in very strict lab conditions after 12 hours fasting. RMR (Resting Metabolic Rate): Measured in less strict conditions, more practical. Both are essentially the same for daily use - typically differ by only 1-2%.