BMI calculator Calculate BMI from your height and weight. What is BMI? It is a body mass index estimated from weight and height. Weight (kg) ÷ calculated by height (m) squared. World Health Organization (WHO) standards state BMI indicators Severe Thinness < 16.00 Moderate Thinness 16.00 - 17.00 Mild Thinness 17.00 - 18.50 Normal 18.50 - 25.00 Overweight 25.00 - 30.00 Obese (Ⅰ) 30.00 - 35.00 Obese (Ⅱ) 35.00 - 40.00 Obese (Ⅲ) ≥ 40.00