How to Calculate BMI
BMI (Body Mass Index) is a simple measure calculated from your weight and height. In metric units, the formula is BMI = weight (kg) / height (m)². In imperial units, the formula is BMI = 703 × weight (lbs) / height (inches)². Enter your weight and height above and your BMI is calculated instantly. The result falls into one of four categories: Underweight (below 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), or Obese (30 and above).
BMI Categories Reference
The World Health Organization defines four BMI categories for adults: Underweight is below 18.5, Normal weight is 18.5 to 24.9, Overweight is 25 to 29.9, and Obese is 30 or above. BMI is a screening tool, not a diagnostic measure. Factors like muscle mass, age, sex, and ethnicity affect body composition independently of BMI. Always consult a healthcare professional for a full health assessment.
Frequently Asked Questions
Is BMI accurate for everyone?
BMI is a useful screening tool but has limitations. It does not account for muscle mass, bone density, age, or fat distribution. Athletes with high muscle mass may have a high BMI but low body fat. Children and the elderly require different reference ranges. Use BMI as one data point, not a definitive health verdict.
Is my data safe?
Yes. This tool runs entirely in your browser using JavaScript. No data is sent to any server. You can verify this by disconnecting from the internet — the calculator will still work.