BMI Calculator

BMI (Body Mass Index) is a numerical value calculated from your height and weight. It is used as a screening tool to categorize individuals as underweight, normal weight, overweight, or obese. It was developed by Belgian mathematician Adolphe Quetelet in the 19th century and is widely used in clinical and public health settings.

BMI is calculated by dividing your weight in kilograms by the square of your height in meters: BMI = weight (kg) / height (m)². In imperial units, the formula is BMI = 703 × weight (lbs) / height (in)². For example, a person who is 70 kg and 1.75 m tall has a BMI of 70 / (1.75²) ≈ 22.9.

According to the World Health Organization (WHO), a BMI between 18.5 and 24.9 is considered normal or healthy weight. BMI below 18.5 is classified as underweight, 25-29.9 as overweight, and 30 or above as obese. Different thresholds apply for children and for certain ethnic groups, particularly South and East Asian populations.

Yes. BMI does not directly measure body fat, so it can be misleading in certain groups. Athletes and highly muscular individuals may have a high BMI despite low body fat. Older adults may have a normal BMI but carry excess visceral fat. It also does not account for fat distribution, bone density, or sex differences in body composition. It is best used alongside other measurements such as waist circumference.

A BMI of 30 or higher is classified as obese. Obesity is associated with an increased risk of type 2 diabetes, heart disease, stroke, sleep apnea, certain cancers, and joint problems. Class I obesity is 30-34.9, Class II is 35-39.9, and Class III (severe or morbid obesity) is 40 and above. If your BMI falls in this range, speaking with a healthcare provider about a tailored management plan is recommended.