BMI Calculator
Calculate your Body Mass Index with detailed interpretation.
⚠️ BMI is an estimate and does not replace professional medical assessment.
What is BMI
Body Mass Index (BMI) is a measure created by Belgian statistician Adolphe Quetelet in the 19th century, still used by the World Health Organization (WHO) as an initial screening to classify weight relative to height. It is calculated by dividing weight in kilograms by height in meters squared (BMI = weight / height²).
BMI is a population-level indicator: it does not distinguish muscle mass from body fat, and does not account for fat distribution, age, sex, or body type. Athletes with a lot of lean mass, for example, can show a high BMI without excess fat. Treat the result as a starting point, not a diagnosis.
How to interpret the result
The WHO standard classification considers below 18.5 as underweight, 18.5 to 24.9 as normal weight, 25 to 29.9 as overweight, and 30 or above as different degrees of obesity. These ranges are a general reference for adults and do not apply the same way to children, pregnant women, or older adults.
Frequently asked questions
Is BMI reliable for everyone?
Not entirely. It is a good population-level indicator, but it can distort results for athletes, older adults, pregnant women, and very muscular people. For a complete assessment, it is best to combine BMI with other measures, such as body fat percentage and waist circumference.
What is the ideal BMI?
The WHO healthy range for adults is 18.5 to 24.9. Within that range, the "ideal" value varies by age, body composition, and health history.
How is BMI calculated?
The formula is weight (kg) divided by height (m) squared. For example, a person weighing 70 kg at 1.70 m has a BMI of 70 / (1.70 × 1.70) ≈ 24.2.
Does a high BMI mean obesity?
Not necessarily. A high BMI indicates overweight by the formula, but an obesity diagnosis should be made by a health professional considering other factors beyond weight and height.