BMI Calculator
Body Mass Index — metric & imperial
About BMI Calculator
What is BMI?
Body Mass Index (BMI) is a simple ratio of weight to height that places adults into broad weight categories. It's a screening tool — not a diagnosis — used by doctors and public-health agencies worldwide.
BMI categories (adults, WHO)
- Below 18.5 — Underweight
- 18.5 – 24.9 — Healthy
- 25.0 – 29.9 — Overweight
- 30.0 and above — Obese
What BMI does NOT account for
BMI doesn't distinguish between muscle and fat, doesn't reflect body-fat distribution, and is less reliable for athletes, older adults, and pregnant people. Use it as one signal, not the only one.
Frequently asked questions
Metric: weight (kg) ÷ height (m)². Imperial: (weight in lb ÷ height in inches²) × 703.
Not always. Muscular people often score "overweight" because muscle weighs more than fat. Use body-fat percentage as a complement.
Not directly — children use BMI percentiles for their age and sex, not the adult categories.
For most adults, 18.5–24.9. But individual factors (muscle mass, age, ethnicity) matter; ask your doctor about you specifically.
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BMI Calculator
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