Formula
WHO: weight (kg) divided by height (m) squared. Imperial uses 703 × lb ÷ inches².
BMI Calculator
Calculate Body Mass Index using WHO international weight categories. Instant underweight, normal, overweight, or obesity classification.
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About this method
Categories
Underweight <18.5 · Normal 18.5–24.9 · Overweight 25–29.9 · Obese ≥30 (adult WHO-style bands).
Limitations
Does not account for muscle mass, bone density, pregnancy, or ethnicity-specific risk. Screening only.
Frequently asked questions
What is a healthy BMI?
For most adults, WHO bands are: underweight under 18.5, normal 18.5–24.9, overweight 25–29.9, and obese 30 or higher. Athletes, pregnancy, older adults, and some ethnic groups may need different interpretation.
How is BMI calculated?
BMI = weight in kilograms divided by height in metres squared. Imperial: BMI = 703 × weight (lb) ÷ height (inches)².
Is BMI medical advice?
No. BMI is a population screening number. It does not measure body fat, muscle, or metabolic health. Discuss results with a clinician.
Does BMI work for children?
Children and teens use age- and sex-specific BMI percentiles, not adult cut-offs. This tool is designed for adults.