BMI Calculator

How BMI is calculated

BMI = weight (kg) ÷ height (m)². It's a quick screening number that sorts adults into categories: underweight (<18.5), normal (18.5–24.9), overweight (25–29.9), and obese (30+). BMI is a useful general indicator but doesn't distinguish muscle from fat, so athletes and some body types may read high without excess fat. Treat it as a starting point, not a diagnosis.

The categories at a glance

• Under 18.5: underweight
• 18.5–24.9: normal / healthy weight
• 25–29.9: overweight
• 30 and above: obese

What BMI is good for — and its limits

At a population level, higher BMI correlates with higher risk of conditions like type 2 diabetes and heart disease, which is why clinicians use it as a fast first screen. But BMI only knows your height and weight — it can't tell muscle from fat or where fat sits. Muscular athletes often read "overweight" despite low body fat, and it doesn't account for waist size, which matters for health risk. Use it as a conversation starter alongside other measures, not a verdict. Our guide on how to calculate your BMI and what it means goes further.

Private and instant

Switch between metric and imperial units and get your BMI and category immediately. Your height and weight stay in your browser — they're never uploaded or stored.

This tool provides general information, not medical advice. For guidance about your health, consult a qualified professional.