Calculate BMI and read what the band means
Height and weight to a BMI, its WHO category, and the weight range that would be “normal” at that height — plus where the number stops being useful.
Tools used in this guide
The job
BMI compresses height and weight into one screening number: weight in kilograms divided by height in meters squared. It is the standard first-pass check on health forms and fitness apps.
The bands
Below 18.5 is underweight, 18.5–25 is the normal range, 25–30 is overweight, and 30 and above is obese. These are the WHO bands that Japan also uses. The tool also shows the weight range corresponding to BMI 18.5–25 at your height, which is more actionable than the index alone.
Where BMI stops
BMI cannot tell muscle from fat — a muscular athlete and a sedentary person can share the same number. It also ignores fat distribution and age. Use it as a screening signal, not a diagnosis, and combine it with waist size or a doctor’s measurement when it matters.