TDEE Calorie & Macronutrient Forecaster
Simulate energy expenditure schedules. Calculate Basal Metabolic Rate, Total Daily Energy Expenditure, and customize macronutrient ratios for deficit, maintenance, or surplus splits.
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AmortizationUnderstanding TDEE, BMR, and Caloric Splits
BMR vs. TDEE: What is the difference?
Your **Basal Metabolic Rate (BMR)** represents the baseline calories your body burns at complete, vegetative rest simply to perform basic autonomic functions (breathing, circulating blood, cellular repair). Your **Total Daily Energy Expenditure (TDEE)** incorporates your activity multiplier, showing the total number of calories you burn daily to support all physical movements and workouts.
Mifflin-St Jeor vs. Katch-McArdle models
The **Mifflin-St Jeor** equation calculates BMR using age, gender, height, and total body weight. The **Katch-McArdle** equation calculates BMR entirely based on your **lean body mass** (excluding body fat weight). Katch-McArdle is highly precise for muscular individuals or those who know their body fat percentage, as muscle tissue consumes significantly more energy than fat tissue.
How do macronutrient splits influence composition?
While calories determine whether you lose or gain weight, **macronutrients** (protein, carbs, and fats) determine *what* kind of weight you gain or lose. High protein protects skeletal muscle mass in a deficit and aids recovery. Carbohydrates supply immediate glycogen energy for training, and fats support cellular structure and hormone regulation.
A Worked Example
Take a 30-year-old man who is 5'10" (178 cm) and 180 lb (81.6 kg). Using the Mifflin-St Jeor equation his BMR is about 1,784 calories — the energy he'd burn at complete rest.
If he's moderately active (exercising 3–5 days a week) we multiply by roughly 1.55, giving a TDEE near 2,765 calories a day to maintain weight. To lose about a pound a week he'd aim for a 500-calorie deficit — around 2,265 a day — while keeping protein high to preserve muscle. Because TDEE is an estimate, the smart move is to track your weight for two weeks and adjust intake by 100–200 calories from there.
Frequently Asked Questions
How big a calorie deficit should I use to lose weight?
A deficit of about 500 calories a day typically yields roughly one pound of fat loss per week. Larger deficits speed results but are harder to sustain and can cost muscle mass.
How much protein should I eat?
A common target is 0.7–1 gram of protein per pound of body weight (or lean mass), especially while in a calorie deficit, to protect muscle and support recovery.
Why isn't my weight changing at my calculated TDEE?
TDEE is an estimate; real expenditure varies with daily movement, metabolism, and tracking accuracy. If your weight is stable, adjust intake by 100–200 calories and reassess after a couple of weeks.