BMI Calculator

In metric: BMI = weight(kg) ÷ height(m)². In imperial: BMI = 703 × weight(lb) ÷ height(in)². So a person who is 175 cm tall and weighs 70 kg has a BMI of 70 ÷ (1.75)² = 22.9, which falls in the Normal range.

The WHO classifies BMI into four main categories: Underweight (below 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), and Obese (30 and above). Some health systems use additional sub-categories within the obese range.

BMI is a useful population-level tool but it has real limitations for individuals. It doesn't distinguish between muscle and fat, so athletes with high muscle mass often score as "overweight." It also doesn't reflect where fat is distributed on the body — abdominal fat is generally more harmful than fat on the hips or thighs.

Children, pregnant women, and the elderly require different reference ranges. Certain ethnic groups also have health risks at lower BMI thresholds. Always use BMI as a starting point for a conversation with your doctor, not as a diagnosis.

• Is BMI the same for men and women? The calculation is identical, but the health implications can differ. Muscle mass, fat distribution, and bone density vary by sex, so doctors often interpret BMI results differently for men and women.
• What BMI is considered healthy? The WHO defines 18.5–24.9 as normal weight. However, optimal BMI can vary by age and ethnicity — some Asian health guidelines use lower thresholds (23 for overweight, 27.5 for obese).
• Can I be healthy with a high BMI? Yes. BMI is one data point. Fitness level, diet quality, blood pressure, blood sugar, and other metabolic markers all factor into health. An overweight person who exercises regularly can be metabolically healthier than a normal-weight sedentary person.