Calculate your Body Mass Index and find your WHO category.
The Body Mass Index (BMI) is a metric that describes the ratio of body weight to height. It is calculated by dividing weight in kilograms by height in meters squared. BMI serves as a rough guide to assess whether a person is underweight, normal weight, or overweight, and is used by the World Health Organization (WHO) as a standard indicator.
BMI does not distinguish between muscle and fat mass. Athletes with high muscle mass may have a high BMI while being healthy. Similarly, BMI does not account for age, sex, body frame or fat distribution. It should therefore be considered a starting point — for a comprehensive assessment, medical consultation is recommended.
The Body Mass Index was introduced in 1832 by the Belgian mathematician Adolphe Quetelet — originally not as a medical test but as a population statistic. It was Ancel Keys, an American physiologist, who coined the term 'Body Mass Index' in a 1972 paper in the Journal of Chronic Diseases and showed that weight divided by height squared correlates better with body fat percentage than other indices used at the time. The World Health Organization (WHO) adopted the thresholds 18.5 / 25 / 30 as a reference for epidemiological comparisons in the 1990s.
BMI is therefore a rough approximation of body composition from two easy-to-measure numbers. It says nothing about how much muscle, fat or water you carry. A bodybuilder at 95 kg and 1.80 m has a BMI of 29.3 — formally 'overweight', even though his body-fat percentage might be below 10%. Conversely, a sedentary person with BMI 23 can carry an elevated visceral fat load. Studies such as the NHANES analyses show that at population level BMI still correlates well with risk for diabetes, cardiovascular disease and all-cause mortality — at the individual level it is a coarser instrument.
For a more precise picture, physicians and nutritionists complement BMI with waist-to-hip ratio (WHR), waist circumference, bioelectrical impedance analysis (BIA) or DEXA scans. Nevertheless BMI remains the global screening tool — cheap, reproducible and internationally comparable. This page provides a pure calculation using WHO thresholds and is explicitly not medical advice.
In the metric system, BMI is weight in kilograms divided by the square of height in meters. The US imperial counterpart uses the constant 703 to convert pounds and inches into the same dimensionless figure. The healthy weight range is obtained by multiplying the BMI bounds 18.5 and 24.9 by the square of your own height.
BMI (metric) = weight_kg / (height_m)^2
BMI (imperial) = (weight_lbs * 703) / (height_in)^2
Healthy weight = 18.5 .. 24.9 * (height_m)^2
Example: 1.75 m
low = 18.5 * 1.75^2 = 56.7 kg
high = 24.9 * 1.75^2 = 76.3 kgFive typical scenarios, each with BMI, category and healthy weight range:
Do not rely on BMI if you are a bodybuilder, strength athlete, elite endurance athlete, pregnant, under 18, very tall or very short (below 1.50 m or above 2.00 m), or carry significant fluid retention, amputations or certain chronic conditions. For people over roughly 65, WHO and national guidelines recommend a slightly higher normal range (BMI 22 - 27), because a moderate weight reserve correlates with better survival. Children have separate BMI percentiles by age and sex. This page is an informational calculation and does not replace a medical diagnosis; if you have health concerns, talk to your physician or a registered dietitian.