Total Daily Energy Expenditure (TDEE) quantifies the cumulative number of kilocalories your body expends in a 24-hour period. It comprises Basal Metabolic Rate (BMR, roughly 60%–70% of energy), Non-Exercise Activity Thermogenesis (NEAT, roughly 15%), the Thermic Effect of Food (TEF, roughly 10%), and Exercise Activity Thermogenesis (EAT, roughly 5%–10%). Estimating TDEE provides the foundational baseline for establishing dietary deficits or surpluses.

### Tool Implementation and Calculation Mechanics The calculator implements the clinically validated Mifflin-St Jeor equation combined with standardized physical activity scaling factors:

- **Mifflin-St Jeor Basal Metabolic Rate (BMR):**\n $\text{BMR} = 10 \times \text{Weight (kg)} + 6.25 \times \text{Height (cm)} - 5 \times \text{Age (years)} + S$\n (where $S = +5$ for biological males, and $S = -161$ for biological females). - **Physical Activity Multipliers:**\n - Sedentary (Desk job, minimal movement): $\text{BMR} \times 1.2$\n - Light Exercise (1–3 days/week): $\text{BMR} \times 1.375$\n - Moderate Exercise (3–5 days/week): $\text{BMR} \times 1.55$\n - Heavy Exercise (6–7 days/week): $\text{BMR} \times 1.725$\n - Athlete / Heavy Physical Labor: $\text{BMR} \times 1.9$ - **Target Caloric Scenarios:**\n - **Weight Maintenance:** $\text{TDEE}$\n - **Standard Fat Loss Cut (-500 kcal):** $\text{TDEE} - 500\text{ kcal/day}$ ($\approx 1\text{ lb / } 0.45\text{ kg loss per week}$)\n - **Lean Muscle Bulk (+300 kcal):** $\text{TDEE} + 300\text{ kcal/day}$ ($\approx 0.5\text{ lb / } 0.25\text{ kg gain per week}$)

### Worked Numeric Example Using the tool default settings: - **Sex:** Male\n- **Age:** 30 years\n- **Body Weight:** 80 kg\n- **Height:** 178 cm\n- **Activity Level:** Moderate Exercise (1.55× multiplier)\n- **Calculation Steps:**\n 1. BMR: $(10 \times 80) + (6.25 \times 178) - (5 \times 30) + 5 = 800 + 1,112.5 - 150 + 5 = 1,767.5\text{ kcal/day}$.\n 2. TDEE: $1,767.5 \times 1.55 \approx 2,740\text{ kcal/day}$.\n 3. Standard Fat Loss Target (-500 kcal): $2,740 - 500 = 2,240\text{ kcal/day}$.\n 4. Lean Bulk Target (+300 kcal): $2,740 + 300 = 3,040\text{ kcal/day}$.

### Clinical Disclaimer & Local Privacy Guarantee Metabolic equations provide population statistical estimates. True energy expenditure is modulated by thyroid hormone levels, lean skeletal muscle percentage, adaptive thermogenesis, and ambient climate. This tool does not diagnose metabolic disorders. All calculations execute client-side in browser memory with zero network data transmission.