Total Daily Energy Expenditure (TDEE) and Basal Metabolic Rate (BMR) calculations provide the scientific foundation for nutritional planning. By estimating the exact energy required to sustain life-support systems (BMR) and accounting for physical movement (TDEE), individuals can dynamically adjust their caloric intake to maintain, lose, or gain body mass. This calculator implements three clinically validated equations—Mifflin-St Jeor, Revised Harris-Benedict (1984), and the lean body mass-based Katch-McArdle formula—combined with standardized physical activity multipliers to map daily energy requirements, while enforcing metabolic safety thresholds to prevent starvation-mode nutrition deficits.
Mathematical Formula & Logic
Daily caloric needs are modeled through Basal Metabolic Rate (BMR) scaled by a Physical Activity Level (PAL) coefficient and adjusted for weight goals:
1. Basal Metabolic Rate (BMR):
- Mifflin-St Jeor (Default):
Men: BMR = 10 × Weight (kg) + 6.25 × Height (cm) - 5 × Age (years) + 5
Women: BMR = 10 × Weight (kg) + 6.25 × Height (cm) - 5 × Age (years) - 161
- Revised Harris-Benedict (1984):
Men: BMR = 88.362 + 13.397 × Weight (kg) + 4.799 × Height (cm) - 5.677 × Age (years)
Women: BMR = 447.593 + 9.247 × Weight (kg) + 3.098 × Height (cm) - 4.330 × Age (years)
- Katch-McArdle (Body Fat % Known):
BMR = 370 + 21.6 × Lean Body Mass (LBM)
Where LBM = Weight (kg) × (1 - Body Fat % / 100)
2. Total Daily Energy Expenditure (TDEE):
TDEE = BMR × PAL
PAL Factors: Sedentary (1.2), Light (1.375), Moderate (1.55), Active (1.725), Extra Active (1.9)
3. Weight Goal Adjustments:
- Maintain Weight: Target = TDEE
- Weight Loss: Mild (-250 kcal/day), Standard (-500 kcal/day), Extreme (-1000 kcal/day)
- Weight Gain: Mild (+250 kcal/day), Standard (+500 kcal/day), Extreme (+1000 kcal/day)
Note: Target calories are flagged with a clinical safety warning if they fall below 1,200 kcal/day for women or 1,500 kcal/day for men.
Step-by-Step Example
Calculate daily target calories for a 30-year-old male who stands 175 cm tall, weighs 70 kg, has 15% body fat, is moderately active (PAL multiplier 1.55), and wants to lose weight (standard rate):
1. Calculate BMR using Mifflin-St Jeor:
BMR = 10 × 70 + 6.25 × 175 - 5 × 30 + 5 = 700 + 1093.75 - 150 + 5 = 1648.75 kcal/day
2. Calculate TDEE:
TDEE = 1648.75 × 1.55 = 2555.56 kcal/day
3. Apply goal deficit (-500 kcal/day for standard weight loss):
Target Calories = 2555.56 - 500 = 2055.56 kcal/day (rounded to 2056 kcal/day).
4. Since 2056 kcal is well above the male safety limit of 1500 kcal, it is a safe caloric target.
Reference Data & Values
activity level
bmr mifflin
tdee
lose standard
Sedentary (1.2)
1,649 kcal
1,979 kcal
1,479 kcal
Lightly Active (1.375)
1,649 kcal
2,267 kcal
1,767 kcal
Moderately Active (1.55)
1,649 kcal
2,556 kcal
2,056 kcal
Very Active (1.725)
1,649 kcal
2,844 kcal
2,344 kcal
Extra Active (1.9)
1,649 kcal
3,133 kcal
2,633 kcal
Frequently Asked Questions
The Mifflin-St Jeor equation is widely recommended for healthy adults and is considered the clinical gold standard for BMR estimation. However, if you know your exact body fat percentage, the Katch-McArdle equation is more accurate because it calculates energy needs using lean body mass.
BMR (Basal Metabolic Rate) is the energy your body needs to survive in a resting state (to breathe and pump blood). TDEE (Total Daily Energy Expenditure) is your BMR multiplied by your physical activity level, reflecting the total calories burned throughout the day.
A safe rate of weight loss is 0.5 to 1 kg (1 to 2 pounds) per week, which requires a daily deficit of 500 to 1,000 calories. However, daily calories should not fall below 1,200 kcal/day for women or 1,500 kcal/day for men unless supervised by a physician.
Severe calorie restriction below clinical limits (1,200 for women, 1,500 for men) can trigger muscle tissue breakdown, vitamin deficiencies, and adaptive thermogenesis (metabolic slowdown), making long-term weight maintenance difficult.
Activity multipliers scale your resting metabolism based on physical movement. They range from 1.2 for sedentary lifestyles (desk jobs) to 1.9 for extra active individuals (athletes or heavy physical labor).
No. The Katch-McArdle formula relies entirely on Lean Body Mass (LBM), which requires knowing your body fat percentage. If you do not know it, use Mifflin-St Jeor or Revised Harris-Benedict instead.
Eating exactly your TDEE calories will keep you in energy balance, meaning you will maintain your current body weight.
As you lose weight, your body mass decreases, which reduces both BMR and active movement energy requirements. You must recalculate your calorie needs at your new weight to keep losing weight.