Calculator
BMI
Calculate an adult body mass index from a height and a weight.
This shows a published reference. It is not a dose to take and it is not personal medical advice.
Questions
Why is there no underweight or normal label?
The opened WHO fact sheet states overweight at 25 or above and obesity at 30 or above. This page does not add other category names.
How this number is made
What this result means
The number is weight in kilograms divided by height in metres squared. At or above 25 is labeled Overweight. At or above 30 is labeled Obesity. A figure below 25 is shown without a category name.
Formula and methodology
Pounds are converted at 0.45359237 kilograms per pound. Inches are converted at 0.0254 metres per inch. The cut points are the adult figures on the WHO fact sheet Obesity and overweight.
Worked example
80 kg at 1.80 m is 24.7, which is below 25, so no category name is shown. 81 kg at 1.80 m is 25.0 and is labeled Overweight. 100 kg at 1.80 m is 30.9 and is labeled Obesity.
Assumptions and limitations
The cut points are for adults age 20 and older. The figure does not separate muscle from fat. It is not a treatment plan and it is not a dose.
Who should not rely on the result
Anyone younger than 20, or anyone who wants this number to decide a treatment, should not use this result as that decision.
Sources
- WHO fact sheet, Obesity and overweight. Accessed 2026-10-05.