BMI Calculator
Calculate your Body Mass Index in metric or imperial. See your BMI value and where it falls on the standard weight classification scale.
<18.5
18.5–24.9
25–29.9
≥ 30
BMI categories and what they mean
| BMI | Category | Health implication |
|---|---|---|
| Below 18.5 | Underweight | May signal malnutrition or other health issues |
| 18.5–24.9 | Normal weight | Associated with lowest health risk |
| 25–29.9 | Overweight | Elevated risk of some chronic diseases |
| 30–34.9 | Obese Class I | High risk |
| 35–39.9 | Obese Class II | Very high risk |
| 40+ | Obese Class III | Extremely high risk |
Frequently asked questions
What is BMI?
BMI (Body Mass Index) is a number calculated from your height and weight. It provides a simple screening tool to indicate whether a person might be underweight, a healthy weight, overweight, or obese. It was developed in the 1830s by Belgian statistician Adolphe Quetelet.
What are the BMI categories?
The WHO standard categories are: Underweight (BMI < 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), and Obese (≥ 30). Some authorities further split obesity into Class I (30–34.9), Class II (35–39.9), and Class III (≥ 40).
Is BMI accurate for everyone?
BMI has limitations. It does not distinguish between muscle and fat, so very muscular people (like athletes) may be classified as overweight despite being healthy. It also doesn't account for age, sex, ethnicity, or where fat is distributed in the body. BMI is a screening tool, not a medical diagnosis.
What BMI is considered healthy?
A BMI between 18.5 and 24.9 is generally considered in the normal or healthy weight range for adults. However, what's 'healthy' varies by individual, and a doctor's assessment is more informative than BMI alone.
How is BMI calculated?
Metric: BMI = weight (kg) ÷ height (m)². Imperial: BMI = 703 × weight (lbs) ÷ height (inches)².
BMI is a screening tool, not a medical diagnosis. Consult a healthcare professional for personalised health advice. CalcOrchard provides this calculator for educational purposes only.