- What is BMR (Basal Metabolic Rate)?
- BMR is the number of calories your body burns at complete rest to maintain vital functions — breathing, circulation, cell production, and organ function. It represents 60–70% of your total daily calorie expenditure. This calculator uses the Mifflin-St Jeor equation, the most accurate BMR formula for most people.
- What is TDEE (Total Daily Energy Expenditure)?
- TDEE is BMR multiplied by an activity multiplier that accounts for physical activity. It represents how many calories you burn in a typical day. To maintain your current weight, eat approximately equal to your TDEE. To lose weight, eat less than your TDEE; to gain muscle, eat slightly more.
- How accurate is the Mifflin-St Jeor equation?
- The Mifflin-St Jeor equation is the most validated BMR formula for adults of healthy weight, predicting BMR within ±10% for most people. It is less accurate for very muscular individuals (underestimates) and those with obesity (overestimates). Actual calorie needs can only be confirmed through metabolic testing.
- How many calories should I eat to lose weight?
- A 500 calorie/day deficit below TDEE creates approximately a 1 pound (0.45 kg) per week loss — the commonly recommended rate. A 250 calorie deficit creates 0.5 lb/week loss. Going below 1,200 calories/day (women) or 1,500/day (men) is not recommended without medical supervision.
- What is the difference between calories and kilocalories?
- In food/nutrition, "calorie" always means kilocalorie (kcal) — 1,000 thermodynamic calories. When a food label says "200 calories," it means 200 kcal. The notation Calorie (uppercase C) technically means kcal, but in everyday use, "calorie" and "kcal" are used interchangeably for food energy.
- What activity level should I select?
- Sedentary: desk job, minimal walking. Lightly active: walking 1–3 days/week or light exercise. Moderately active: cardio 3–5 days/week or a physically moderate job. Very active: intense training 6–7 days/week or a physical job. Extra active: athletic training twice daily or very heavy manual labor.
- What are macros and how are the percentages calculated?
- Macronutrients (macros) are protein, carbohydrates, and fat — the three sources of calories. The suggested split (30% protein, 45% carbs, 25% fat) is a moderate balanced ratio. Protein and carbs provide 4 calories/gram; fat provides 9 calories/gram. Adjusting these ratios for your goals (e.g. higher protein for muscle gain, lower carbs for keto) changes the grams shown.