Calculate your Body Mass Index from weight and height, with the WHO bands and the healthy weight range for your height.
The Body Mass Index divides your weight in kilograms by the square of your height in metres. The idea comes from the Belgian statistician Adolphe Quetelet, who in the 1830s was describing populations rather than diagnosing individuals, and it became the standard screening index when the World Health Organization adopted the current cut-off points for adults in its 1995 and 2000 reports: below 18.5 is underweight, 18.5 to 24.9 is normal weight, 25 to 29.9 is overweight, and 30 upwards is obesity, split into classes I, II and III at 35 and 40. Those thresholds exist because large cohort studies found the lowest rates of cardiovascular disease and all-cause mortality around the middle of that range.
This calculator applies exactly that formula and nothing else. It accepts height in metres or in centimetres and tells you which reading it used, understands the Brazilian decimal comma, and then inverts the equation to show the weight range that would put you between BMI 18.5 and 24.9 for your height — a 1.75 m adult, for example, lands between roughly 56.7 kg and 76.3 kg. The full table of bands is shown with your position highlighted, so you can see how far you are from the neighbouring ranges instead of reading a single isolated number.
It is worth being clear about what this index cannot do. BMI knows only two numbers, so it cannot tell muscle from fat: a well-trained athlete with plenty of lean mass is regularly classified as overweight, while an inactive person with little muscle can sit inside the normal band with a high body fat percentage. It also does not apply to children and teenagers, who need age-and-sex percentile curves, nor to pregnant women, and it becomes less reliable in older adults, whose height shrinks and body composition changes. Cut-off points also vary between populations — several Asian health authorities use lower thresholds. Waist circumference, body composition measurements and blood work say far more about health risk than this single ratio, which is why BMI is a screening signal and never a diagnosis.
BMI = weight (kg) ÷ height (m)². WHO bands for adults: below 18.5 underweight; 18.5 to 24.9 normal weight; 25 to 29.9 overweight; 30 to 34.9 obesity class I; 35 to 39.9 obesity class II; 40 or more obesity class III. The healthy weight range shown is 18.5 × height² to 24.9 × height².
Between 18.5 and 24.9 for adults, according to the World Health Organization. Below 18.5 is classified as underweight, 25 to 29.9 as overweight and 30 or more as obesity, divided into three classes.
Often not. Muscle is denser than fat, so a muscular athlete can weigh enough to be classified as overweight or obese while carrying a low body fat percentage. In that case body composition measurements are far more informative.
No. Children and teenagers are assessed with age-and-sex percentile curves, and pregnancy changes weight for reasons the index cannot interpret. Older adults should also read the result with care, since height and body composition change with age.
It is the BMI formula solved backwards: 18.5 × height² gives the lower bound and 24.9 × height² the upper one. It is a statistical range, not a personal target — the right weight for you depends on body composition, health history and what a professional evaluates.
No. The calculation runs entirely in JavaScript on your device. Nothing you type is uploaded, logged or stored anywhere.
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