BMI Calculator

Body Mass Index divides your weight in kilograms by the square of your height in meters. A 75kg person at 1.75m tall has a BMI of 24.5 — classified as normal weight. The WHO categories are: underweight (below 18.5), normal (18.5-24.9), overweight (25-29.9), and obese (30+). BMI was designed in the 1830s by Adolphe Quetelet as a population-level statistical tool, not an individual health diagnostic. Its main limitation is that it cannot distinguish between muscle mass and fat mass. A bodybuilder at 100kg and 1.80m has a BMI of 30.9 (obese) despite potentially having 10% body fat. Similarly, an elderly person losing muscle but maintaining weight might have a normal BMI while actually carrying excess fat. Despite these limitations, BMI remains useful as a quick screening tool because at the population level, higher BMI correlates with increased risk of type 2 diabetes, cardiovascular disease, and certain cancers. This calculator computes your BMI instantly in your browser and explains what your result means in context.

Health risks associated with BMI vary by ethnicity. The WHO suggests that Asian populations face elevated health risks at lower BMI values — a BMI of 23 in an Asian individual carries similar risk to a BMI of 25 in a European individual. This is because body composition differs: at the same BMI, South Asian and East Asian populations tend to carry more visceral fat (around organs) than Europeans. Some countries have adopted adjusted thresholds: Japan uses 25 as the obesity cutoff instead of 30, and Singapore uses 23 as the overweight threshold. For children and adolescents, BMI is interpreted using age-and-sex-specific percentile charts because body composition changes dramatically during growth. A BMI at the 85th percentile for age is classified as overweight, and the 95th percentile as obese. BMI Prime — your BMI divided by 25 — provides another useful metric: a value of 1.0 means you are exactly at the upper limit of normal weight. Values above 1.0 indicate overweight proportional to the excess.