Work out your body mass index from height and weight, in either metric or imperial units, with the standard WHO categories.
Body mass index is a simple ratio of weight to height, used as a population-level screening tool to flag whether someone's weight might fall into an underweight, healthy, overweight, or obese range. It doesn't distinguish muscle from fat, so it's a starting point for conversation, not a diagnosis.
BMI doesn't account for muscle mass, bone density, age, sex, or where fat is distributed on the body. A muscular athlete can register as "overweight" despite having low body fat, and an older adult can have a "healthy" BMI while carrying more fat than muscle. Use it alongside other measures and a conversation with a healthcare provider, not as a standalone verdict.
Not reliably. Because BMI can't tell muscle from fat, very muscular people are often classified as overweight or obese despite having low body fat percentages.
Standard adult BMI categories apply roughly from age 20 onward. Children and teens use age- and sex-specific percentile charts instead, and older adults' healthy range may sit slightly higher.
No — treat it as one data point. Waist circumference, body composition, blood pressure and other markers give a fuller picture, and a doctor can interpret BMI in the context of your overall health.