About BMI Calculator
Calculates BMI, Basal Metabolic Rate (BMR via the Mifflin-St Jeor equation), and Total Daily Energy Expenditure (TDEE) from height, weight, age, gender, and activity level. Supports both metric (kg/cm) and imperial (lbs/ft+in) input. Classifies results into underweight, normal, overweight, and obese categories with associated health risk factors, and calculates your ideal weight range based on the BMI 18.5–24.9 bracket.
- BMI formula: weight (kg) divided by height (m) squared, with automatic unit conversion for imperial input
- BMR uses the Mifflin-St Jeor equation: (10 × weight) + (6.25 × height) – (5 × age) ± gender offset (+5 male, –161 female)
- TDEE calculated by multiplying BMR by one of five activity multipliers: sedentary (1.2), lightly active (1.375), moderately active (1.55), very active (1.725), extra active (1.9)
- Four BMI categories with specific health risk descriptions and dietary/exercise recommendations
- Ideal weight range derived from the healthy BMI bracket (18.5–24.9) applied to your height
Frequently Asked Questions
- How accurate is BMI as a health metric?
- BMI is a population-level screening tool, not a diagnostic. It doesn’t distinguish muscle from fat—a lean athlete and an overweight sedentary person can have the same BMI. Use it as a rough indicator alongside body fat percentage for better context.
- Why Mifflin-St Jeor over Harris-Benedict?
- Mifflin-St Jeor (1990) has been shown in multiple studies to be more accurate for modern populations than the original Harris-Benedict equation (1919). It’s the formula most registered dietitians use today.