BMI Calculator
Body mass index from your height and weight, in US or metric units, with the standard adult categories — and an honest note about what BMI can and can't tell you. Informational only, not medical advice.
| Category | BMI range |
|---|---|
| Underweight | Below 18.5 |
| Normal | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese | 30.0 and above |
How to use this tool
- Choose US or metric units.
- Enter your height and weight.
- Read your BMI and where it falls among the standard categories.
How it works
BMI = weight (kg) ÷ height (m)². In US units the equivalent is 703 × weight (lb) ÷ height (in)². The standard adult categories are: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30+ obese.
Know what BMI is and isn't: it's a population-level screening measure, not a diagnosis. It can't tell muscle from fat — athletes often read 'overweight' with low body fat — and it doesn't apply to children, during pregnancy, or uniformly across all body types. Treat it as one data point, and talk to a healthcare professional about what it means for you.
Sources & references
Content last reviewed: July 2026.
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Frequently asked questions
What is a healthy BMI?
For most adults, 18.5–24.9 is classed as the normal range by the WHO and CDC. But healthy weight is individual — BMI is a screening number, not a verdict.
Is BMI accurate for athletes?
Often not. Muscle is denser than fat, so muscular people frequently score 'overweight' while being lean. Body-fat percentage or waist measurements are better signals in that case.
Does this work for children?
No — pediatric BMI uses age- and sex-specific percentile charts, which this adult calculator doesn't implement. Use the CDC's child and teen BMI tools instead.