BMI Calculator
Calculate your Body Mass Index (BMI) from your height and weight in metric or imperial units. Your BMI and weight category update live as you type.
How to Use the BMI Calculator
- Choose your preferred unit system: Metric (kg/cm) or Imperial (lb/ft-in).
- Enter your height and weight in the fields shown.
- Your BMI number and weight category (Underweight, Normal, Overweight or Obese) appear instantly.
Why Use This Tool?
How is BMI calculated?
BMI is calculated as weight in kilograms divided by height in meters squared (BMI = kg / m²). For imperial inputs, the tool converts height and weight to metric first, then applies the same formula, so results match the standard BMI formula used worldwide by health organizations.
What do the BMI categories mean?
Based on World Health Organization reference ranges: below 18.5 is classified as Underweight, 18.5–24.9 as Normal weight, 25–29.9 as Overweight, and 30 or above as Obese. These ranges are population-level guidelines and don't account for individual factors like muscle mass, bone density, age or sex.
Is BMI a reliable measure of health?
BMI is a widely used general screening tool, not a diagnostic measurement. It doesn't distinguish between muscle and fat, and can misclassify athletes, older adults, pregnant women or people with certain body compositions. This calculator provides a general estimate for informational purposes only — it is not medical advice or a diagnosis. Always consult a doctor or qualified healthcare professional to assess your health and body composition properly.
Is my health data stored anywhere?
No. All calculations happen locally in your browser using JavaScript. Your height and weight are never uploaded, logged or stored — nothing leaves your device.