BMI Calculator
Get your Body Mass Index and category from height and weight.
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Calculate your Body Mass Index (BMI) from your height and weight, in either metric (cm/kg) or imperial (ft-in/lb) units. The tool shows your BMI value and the standard category - underweight, normal, overweight or obese - with a clear visual scale. It is a quick general reference and is calculated instantly in your browser.
What BMI is measuring
Body Mass Index compares your weight against your height using a single formula, giving a number that sorts most adults into a broad category. It became standard because it is quick, needs no equipment, and works well enough across large populations. That is exactly what it was designed for: describing groups, not diagnosing individuals.
Where it stops being useful
BMI does not know the difference between muscle and fat. A trained athlete can land in the overweight range while carrying very little fat, and someone with low muscle mass can sit in the normal range while not being especially healthy. It also says nothing about where weight is carried, which matters medically, and the standard ranges fit some ethnic groups better than others. Treat the number as one rough signal among several, not a verdict.
The standard adult ranges
- Under 18.5: underweight
- 18.5 to 24.9: normal weight
- 25 to 29.9: overweight
- 30 and above: obese
- These apply to adults. Children and teenagers are measured against age and sex percentile charts instead.
How to use BMI Calculator
- 1
Choose metric or imperial units.
- 2
Enter your height and weight.
- 3
Read your BMI value and category.
Frequently asked questions
BMI is your weight in kilograms divided by the square of your height in metres (kg/m²). Imperial values are converted automatically.