How BMI is calculated
BMI is weight in kilograms divided by height in meters squared. Someone who is 70 kg and 175 cm tall has a BMI of 70 ÷ 1.75² ≈ 22.9.
BMI categories for adults
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25 to 29.9 | Overweight |
| 30 or above | Obesity range |
BMI is a screening tool, not a diagnosis. It doesn't separate muscle from fat and isn't meant for children, pregnancy or elite athletes. Speak to a doctor or dietitian for personal health advice.
BMI by age and gender
For adults, BMI uses the same formula and the same categories regardless of age or gender. Men and women can carry different amounts of body fat at the same BMI, but the calculation does not change.
For children and teens (ages 2 to 19), health authorities such as the CDC compare BMI with growth charts for the same age and sex, so this adult calculator is not suitable for them. Some guidelines also use different cut-offs for some ethnic groups.
📖 Guide: What Is BMI? How It's Calculated and Where It Falls Short
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Frequently asked questions
What is a healthy BMI?
For most adults, 18.5 to 24.9 is considered the healthy range.
Is BMI accurate?
It is a quick estimate based only on height and weight, so it can misjudge very muscular people and others. Use it as a starting point, not a verdict.
Does BMI depend on age or gender?
For adults, no. The formula and categories are the same for all adults. Children and teens are assessed with age- and sex-specific charts.
Can I use this BMI calculator for a child?
No. Use a pediatric growth chart or ask a doctor.
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