BMI Calculator
Work out your body mass index in metric or imperial units, see which WHO category it falls into, and the healthy weight range for your height. Calculated entirely in your browser — nothing you enter is sent anywhere.
BMI categories
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5–24.9 | Healthy weight |
| 25.0–29.9 | Overweight |
| 30.0 and above | Obesity |
World Health Organization classification for adults aged 20 and over.
Frequently asked questions
What is BMI?
Body mass index (BMI) is weight divided by height squared. It’s a quick, free screening tool doctors and researchers use to flag whether someone’s weight might be a health risk — not a diagnosis on its own.
How is BMI calculated?
Metric: BMI = weight in kilograms ÷ (height in metres)². Imperial: BMI = 703 × weight in pounds ÷ (height in inches)². This calculator does the arithmetic for you in either unit.
Is BMI accurate for everyone?
No — it doesn’t distinguish muscle from fat, so very muscular people are often flagged as "overweight" despite low body fat, and it can under-read frail older adults with low muscle mass. It also isn’t validated for pregnant people or children. See our page on BMI’s limitations for what to use instead.
What is a healthy BMI?
For most adults, 18.5–24.9 is considered a healthy range. The calculator shows the exact weight range for your height.
Does BMI apply to children?
Not this version. Children and teens are assessed against age- and sex-specific growth-chart percentiles, not the fixed adult categories above — this calculator is for adults 20 and over.
BMI has real limitations — see our page on what BMI does and doesn't tell you for when to look at other measures instead.
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