BMI + Calorie & Macro Calculator
Calculate your BMI, basal metabolic rate, daily energy needs, and target calories for weight goals using the WHO + Mifflin-St Jeor formulas.
Daily Macros (40% carb / 30% protein / 30% fat)
Sources: WHO (BMI categories), Mifflin-St Jeor 1990 (BMR formula), Harris-Benedict 1984 (activity multipliers).
Frequently Asked Questions
Why use Mifflin-St Jeor instead of Harris-Benedict?▾
Mifflin-St Jeor (1990) is more accurate for modern populations than Harris-Benedict (1919). Studies show it predicts BMR within 5% for 82% of people, vs 69% for Harris-Benedict. American Dietetic Association now recommends Mifflin-St Jeor as standard.
What's the difference between BMR and TDEE?▾
BMR (Basal Metabolic Rate) = calories your body burns at complete rest just to stay alive. TDEE (Total Daily Energy Expenditure) = BMR × activity multiplier — actual calories burned including movement. TDEE is what you should base diet on.
How accurate is BMI for athletes?▾
BMI doesn't distinguish muscle from fat. Athletes with high muscle mass often register as 'overweight' or 'obese' despite low body fat. For more accuracy, use body fat percentage (DEXA scan, Bod Pod, or measurements) or waist-to-height ratio.
Why 500 kcal deficit for weight loss?▾
1 kg fat ≈ 7,700 kcal. 500 kcal/day deficit × 7 days = 3,500 kcal/week ≈ 0.5 kg/week loss. This is the safest sustainable rate. Faster loss (>1 kg/week) loses muscle and slows metabolism.
Should I follow these macros exactly?▾
These are baseline (40/30/30 — balanced). Adjust per goal: low-carb diet 20/35/45, high-protein 35/35/30, athletic endurance 60/15/25. Most important is hitting calorie target and minimum protein (1.6-2.2g/kg body weight).