The Macro Split & TDEE Calorie Sizer combines biometric energy expenditure modeling with bodyweight-anchored macronutrient allocation. Rather than applying arbitrary percentage splits to a pre-chosen calorie figure, this calculator first predicts your metabolic baseline, applies physical activity multipliers, adjusts for your specific weight goal, and sets protein intake based on total body mass.

### Tool Implementation and Calculation Mechanics The tool evaluates five personal biometric parameters to generate an integrated daily nutritional prescription:

- **Mifflin-St Jeor BMR Prediction (Standardized Male Baseline):**\n - Weight in kg = $\text{Weight in lbs} \times 0.453592$\n - Height in cm = $\text{Height in inches} \times 2.54$\n - $\text{BMR} = 10 \times \text{Weight (kg)} + 6.25 \times \text{Height (cm)} - 5 \times \text{Age} + 5$\n- **Total Daily Energy Expenditure (TDEE):**\n $\text{TDEE} = \text{Round}(\text{BMR} \times \text{Activity Multiplier})$\n (Multiplier scales: Sedentary = 1.2, Moderate 3–5 days = 1.55, Very Active = 1.725). - **Target Caloric Adjustment:**\n $\text{Target Calories} = \text{TDEE} + \text{Goal Delta}$\n (Goal options: Standard Deficit = -500 kcal, Maintenance = 0 kcal, Lean Bulk = +300 kcal). - **Bodyweight-Anchored Macronutrient Gram Formulation:**\n - **Protein:** $1.0\text{ gram per pound of total bodyweight}$ ($4\text{ kcal/g}$).\n - **Fat:** Fixed at $25\%$ of total target calories ($9\text{ kcal/g}$).\n - **Carbohydrates:** Fills all remaining target calories:\n $\text{Carb Grams} = \text{Round}\left(\frac{\text{Target Calories} - (\text{Protein Grams} \times 4) - (\text{Target Calories} \times 0.25)}{4\text{ kcal/g}}\right)$

### Worked Numeric Example Applying the tool default settings: - **Body Weight:** 175 lbs ($79.38\text{ kg}$)\n- **Height:** 70 inches ($177.8\text{ cm}$)\n- **Age:** 30 years\n- **Activity Multiplier:** 1.55 (Moderate Exercise 3–5 days/week)\n- **Goal Delta:** -500 kcal (Standard Fat Loss Deficit)\n- **Calculation Steps:**\n 1. BMR: $(10 \times 79.38) + (6.25 \times 177.8) - (5 \times 30) + 5 = 793.8 + 1,111.25 - 150 + 5 \approx 1,760\text{ kcal/day}$.\n 2. TDEE: $\text{Round}(1,760 \times 1.55) = 2,728\text{ kcal/day}$.\n 3. Target Daily Calories: $2,728 - 500 = 2,228\text{ kcal/day}$.\n 4. Protein Target: $175\text{ lbs} \times 1.0\text{ g/lb} = 175\text{ grams}$ ($700\text{ kcal}$, representing $31.4\%$ of intake).\n 5. Fat Target: $(2,228 \times 0.25) / 9 = 557\text{ kcal} / 9 \approx 62\text{ grams}$.\n 6. Carbohydrate Target: $(2,228 - 700 - 557) / 4 = 971\text{ kcal} / 4 \approx 243\text{ grams}$.\n 7. Composite Result: **2,228 kcal/day (175g Protein | 243g Carbs | 62g Fat)**.

### Clinical Notice & Local Processing Guarantee Energy expenditure formulas and fixed protein multipliers provide structured empirical targets for athletic training. Individual metabolic adaptation, hormonal status, and non-exercise activity thermogenesis (NEAT) vary significantly. Caloric adjustments should be monitored over two-to-four-week weight trends. This tool does not provide medical diagnoses or replace clinical dietetics. All biometric inputs process strictly client-side in your local browser runtime with zero remote server data retention.