BMI Calculator
Calculate your Body Mass Index (BMI) using metric or imperial units, see BMI category indicators, health risks, your ideal weight range, and learn about BMI interpretation.
BMI Categories
| Category | BMI Range (kg/m²) | Health Risk |
|---|---|---|
| Underweight | < 18.5 | Malnutrition risk |
| Normal weight | 18.5 – 24.9 | Low risk |
| Overweight | 25.0 – 29.9 | Enhanced risk |
| Obesity Class I | 30.0 – 34.9 | Moderate risk |
| Obesity Class II | 35.0 – 39.9 | Severe risk |
| Obesity Class III | ≥ 40.0 | Very severe risk |
- BMI is a screening tool, not a definitive measure of health or body composition.
- Muscle mass, ethnicity, age, and sex can affect interpretation. Consult a healthcare provider for a full assessment.
- BMI may misclassify athletes and older adults.
- See the chart for a quick category lookup and explanation.
BMI: Understanding and Limitations
What is BMI?
BMI (Body Mass Index) is a simple index of weight-for-height that is commonly used to classify underweight, normal weight, overweight, and obesity in adults. It's calculated as weight divided by the square of height (kg/m2).
Origins & Use:
BMI is widely used for population health assessment because it's easy to calculate, but it's an imperfect tool for individuals.
Limitations:
- Does not differentiate between fat and muscle mass
- May misclassify muscular people as overweight or obese
- Does not account for age, sex, ethnicity, or fat distribution
- Not valid for children, pregnant women, the elderly, or certain ethnic groups
Health Risks:
A higher BMI is associated with increased risk of conditions like heart disease, type 2 diabetes, sleep apnea, and more. Underweight is linked to malnutrition, osteoporosis, and immunity issues.
How to Improve BMI:
- Adopt a balanced, nutritious diet
- Increase physical activity
- Consult your healthcare provider for personalized advice
BMI formula: BMI = weight (kg) / [height (m)]² or BMI = 703 × weight (lb) / [height (in)]²