BMI Calculator

Your BMI falls into one of several standard categories defined by the World Health Organization (WHO). A BMI under 18.5 is classified as underweight, which may indicate malnutrition or an underlying health condition. A BMI between 18.5 and 24.9 is considered normal weight and is generally associated with the lowest health risks. A BMI of 25 to 29.9 falls in the overweight range and may signal increased risk for conditions like heart disease and type 2 diabetes. A BMI of 30 or above is classified as obese — further divided into Class I (30–34.9), Class II (35–39.9), and Class III (40+) — and carries a significantly elevated risk of metabolic and cardiovascular disease.

Keep in mind that BMI is a population-level screening metric, not a diagnosis. Two people with the same BMI can have very different body compositions, fitness levels, and health profiles. Your result should be interpreted alongside other measurements and clinical context.

BMI is most useful as a quick, first-pass screening tool during routine health check-ups or when you want a general sense of whether your weight is proportionate to your height. Clinicians commonly use it in primary care, public health surveillance, and epidemiological research to identify individuals who may benefit from further evaluation.

It is also helpful for tracking weight trends over time — for example, monitoring changes during a weight management program or after a lifestyle intervention.

BMI does not distinguish between fat mass and lean mass. Athletes and individuals with high muscle mass may be classified as overweight or obese despite having low body fat. Conversely, older adults who have lost muscle mass may have a normal BMI but carry excess fat.

BMI also does not reflect fat distribution. Central (abdominal) obesity is a stronger predictor of cardiovascular risk than overall weight, and BMI misses this distinction entirely. Waist circumference or waist-to-hip ratio may be more informative in these cases.

Additionally, standard BMI thresholds were developed primarily from data on European populations. The WHO recommends lower cut-offs for some Asian populations (overweight ≥ 23, obese ≥ 27.5) because metabolic risk increases at lower BMI levels in these groups.