The BMI formula
Weight (kg) ÷ Height (m)²
The same calculation gives a BMI number at any age; the way that number is interpreted depends on age.
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YOUR RESULT BMI screening
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Enter your age, height and weight, then calculate to see your BMI and the appropriate interpretation guidance.
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BMI does not directly measure body fat or distinguish fat mass from muscle mass.
KNOW WHAT THE NUMBER MEANS
BMI is a starting point, not the whole picture.
Use BMI as one screening measure alongside health history, waist measurement, physical activity and an appropriate clinical assessment.
Age matters
For adults aged 20+, adult BMI categories are used. For ages 5–19, WHO BMI-for-age charts require sex and exact age (usually in months); this tool does not yet calculate child z-scores or percentiles.
Important limitations
BMI is not a direct measure of body fat. Muscular individuals, athletes, older adults and people with certain conditions may need a broader assessment.
Adult BMI categories
For adults aged 20 years and over
Underweight< 18.5
Healthy range18.5–24.9
Overweight25.0–29.9
Obesity class 130.0–34.9
Obesity class 235.0–39.9
Obesity class 3≥ 40.0
Health note: This tool is for educational screening only. It does not diagnose a condition or replace personalised advice from a qualified healthcare professional. If you are concerned about your weight or growth, speak with an appropriate healthcare professional.
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