BMI Calculator
Calculate Body Mass Index (BMI) from weight and height. Instant classification underweight, normal, overweight or obese. Runs fully in the browser.
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Tool guide
BMI Calculator: how it works
Practical information to understand the result and use this tool correctly.
About BMI Calculator
BMI (body mass index) is weight in kilograms divided by height in meters squared: BMI = kg / m². If height is in cm, convert to meters first (divide by 100).
Example: 70 kg and 175 cm → 70 / 1.75² ≈ 22.9 (normal range for adults).
WHO adult ranges: under 18.5 underweight; 18.5–24.9 normal; 25–29.9 overweight; 30+ obesity. BMI is a screening number, not a full health diagnosis.
How to use it
- 1Enter weight in kilograms.
- 2Enter height in centimeters.
- 3Read BMI and WHO category.
Frequently asked questions
- How do I calculate BMI with kg and cm?
- BMI = kg ÷ (cm ÷ 100)². Example: 80 kg and 170 cm → 80 / 1.70² ≈ 27.7.
- Is BMI the same for children?
- No. Children and teens need age- and sex-specific charts; adult cut-offs do not apply.
- Is this BMI calculator free?
- Yes. It runs in your browser with no account required.