About BMI
Body Mass Index is a screening number that relates weight to height: weight in kilograms divided by height in meters squared. Health services worldwide, including WHO, use it to flag when weight may pose health risks. This calculator handles metric and imperial units, shows your position on the WHO scale, and — more usefully — the healthy weight range for your height.
How to calculate your BMI
- Pick metric (kg/cm) or imperial (lb/ft-in) units.
- Enter your weight and height.
- Press Calculate BMI to see your number, category and healthy range.
Reading the result fairly
- 18.5 – 24.9 is the WHO "normal weight" band; below is underweight, 25–29.9 overweight, 30+ the obesity range.
- BMI can misjudge individuals: muscular people score "overweight" without excess fat, and older adults can score "normal" while carrying little muscle. Some Asian populations face raised health risks at lower BMI values — several countries use a 23 threshold for overweight.
- Waist measurement, fitness, diet and blood work tell a fuller story than any single number.
- This calculator is general information, not medical advice — for personal guidance, talk to a health professional.
Frequently asked questions
What is a healthy BMI?
WHO defines 18.5–24.9 as the normal-weight range for adults. The calculator also shows the actual weight range that corresponds to your height, which is more actionable than the abstract number.
Is BMI accurate for everyone?
It's a population screening tool, not a diagnosis. Muscular athletes often score 'overweight' with low body fat, and some Asian populations face raised risks at lower BMIs (several countries use 23 as the overweight threshold). Treat it as one indicator among several.
Does the calculator work for children?
This calculator uses adult WHO categories. Children and teens need age- and sex-specific BMI percentile charts — a different method used by pediatricians.