BMI Calculator — Body Mass Index (Metric & Imperial)
About the BMI Calculator
Body Mass Index (BMI) estimates body fat using your weight relative to your height. It is the screening tool used by the World Health Organization to sort adults into underweight, normal, overweight and obese ranges.
Enter your height and weight in whichever units you are comfortable with — centimeters and kilograms, or feet/inches and pounds. The calculator shows your BMI, the category it falls into, and the weight range that would be healthy for your height.
How to use the BMI Calculator
- Pick metric (cm/kg) or imperial (ft/in/lb) units.
- Enter your height and weight.
- Read your BMI, category and healthy weight range, recalculated live as you adjust the numbers.
BMI formula
BMI = weight (kg) ÷ height² (m²) Example: 70 kg ÷ (1.75 m)² = 70 ÷ 3.0625 = 22.9 WHO categories: below 18.5 underweight · 18.5–24.9 normal · 25–29.9 overweight · 30+ obese
Frequently asked questions
Is BMI accurate for everyone?
BMI is a population-level screening tool, not a diagnosis. It does not distinguish muscle from fat, so very muscular athletes often score “overweight”, and it may misjudge older adults and children. Treat it as a starting point and consult a professional for a real assessment.
What is a healthy BMI?
For most adults the WHO healthy range is 18.5 to 24.9. The calculator also shows the exact weight range this corresponds to for your height.
Does the calculator send my data anywhere?
No. The math runs locally in your browser; nothing you type is transmitted or stored.
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