BMI (body mass index) is your weight in kilograms divided by your height in metres squared — a quick screening number used worldwide since the World Health Organization standardised the categories. It costs nothing and needs no equipment, which is why clinics still start with it. Its limits are just as well known: it cannot tell muscle from fat, it says nothing about where fat is carried, and it was built from population averages. Treat your result as a first indicator, and pair it with the Body Fat Calculator or a clinician’s assessment for the fuller picture.
A note on health results: every figure this tool gives is an estimate from a standard formula — it is not medical advice and it does not diagnose anything. Bodies vary, and formulas cannot see your health history. Use the result as a starting point, and consult a clinician or registered dietitian for personal health decisions.
How to use it
Enter your weight — in kilograms or pounds, switchable in one tap.
Enter your height — in centimetres, or feet and inches.
Read your BMI and category — underweight, normal, overweight or obese, by the WHO bands.
Check the healthy range — the weights that would put your height at a BMI of 18.5 to 24.9.
What you get
Both unit systems — kg/cm or lbs/ft-in, converted for you.
WHO categories — underweight below 18.5, normal 18.5–24.9, overweight 25–29.9, obese 30+.
Healthy weight range — worked out for your exact height.
Instant results — updates as you type, nothing uploaded.
Frequently asked questions
What is a healthy BMI?
For adults, the WHO puts the normal range at 18.5 to 24.9. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese. These bands are screening guides for populations, not a diagnosis for an individual.
Why does BMI mislead athletes?
BMI only sees total weight against height. Muscle is denser than fat, so a muscular athlete can land in the overweight band with low body fat — and someone with little muscle can sit in the normal band with high body fat. That is why this result pairs well with a body fat estimate.
What weight should I be for my height?
The calculator shows it directly: the healthy range is the weight band that gives a BMI of 18.5 to 24.9 at your height. It is a range, not a single magic number — anywhere inside it is the normal band.