Adult BMI Calculator

Body mass index is a simple ratio of weight to height. It is useful in population research and can be one starting point in an adult health conversation, but it does not distinguish fat from muscle, bone or fluid, and it does not show where fat is carried. Two people with the same BMI may have different body composition, history, fitness, and health risks. The calculator presents a number alongside three reference frames so that a single label is not mistaken for a complete assessment.

The WHO adult categories use 18.5, 25 and 30 as boundaries for underweight, overweight and obesity ranges. The Indian consensus published in 2009 proposed lower adult action cut-offs: 23 for overweight and 25 for obesity. These are historical consensus thresholds, not a universal or current diagnosis for every person in India. The WHO expert consultation on Asian populations described 23 and 27.5 as public-health action points because risk can rise at lower BMI in some Asian groups; it did not establish one universally correct alternative definition. The thresholds answer different questions and should not be collapsed into one ranking.

This calculator is intended for adults and accepts a broad range of measurement units. It is not appropriate for children or teenagers, for whom age- and sex-specific growth charts are used. Pregnancy changes weight and requires a different context. Athletes and people with unusually high muscle mass can have a BMI that does not reflect body fat; older age, illness, edema and recent weight change also affect interpretation. If a result worries you, discuss it alongside blood pressure, medical history, waist measures and other relevant information with a qualified professional.

A category boundary is not a sudden change in the body. A result close to a cut-off can shift with rounding or measurement error, so use accurate height and weight and treat the displayed decimal as an estimate. Do not use BMI alone to set a target weight, restrict food, or judge whether someone is healthy. The classifications below are descriptive references only. They do not account for personal circumstances, and the tool does not provide treatment advice or promise that changing BMI will produce a particular outcome.