Body mass index formula
BMI = weight in kg ÷ height² in metresGeneral WHO adult references place underweight below 18.5, overweight from 25 and obesity from 30. Individual assessment may require more information.
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HOW IT WORKS
A result to understand, not just read.
Body mass index relates weight to height and is a simple population screening measure. It does not directly measure body fat, muscle mass or the distribution of fat around the body.
FREQUENTLY ASKED QUESTIONS
Does a normal BMI prove that I am healthy?+
No. BMI is one indicator only; waist size, weight trend, blood pressure, test results and medical history can add important context.
Can adult BMI categories be used for children?+
No. Children and teenagers need age- and sex-specific growth references.
RESULT GUIDE
How to calculate and interpret adult BMI
BMI divides weight by height squared. General adult cut-offs are useful for screening populations, but they are not an individual diagnosis or a direct body-fat measurement.
Example: 80 kg at 1.80 m
- weight: 80 kg
- height: 1.80 m
This falls within the mathematical 18.5–24.9 range but does not describe body composition or personal risk on its own.
How to interpret the result
- Treat BMI as a starting signal, not a diagnosis or judgement about a person’s body.
- BMI can overestimate body fat in very muscular people.
What the estimate does not include
- Adult cut-offs are not suitable for pregnancy, children or certain clinical situations.
- A weight corresponding to a BMI range is not automatically an individual’s ideal weight.
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