BMI Calculator
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📊 BMI Categories (WHO Standard)
| BMI Range | Category | Health Risk |
|---|---|---|
| < 18.5 | Underweight | Low (other risks) |
| 18.5 – 24.9 | Normal weight | Minimal |
| 25.0 – 29.9 | Overweight | Increased |
| 30.0 – 34.9 | Obese (Class I) | High |
| 35.0 – 39.9 | Obese (Class II) | Very High |
| ≥ 40.0 | Obese (Class III) | Extremely High |
What is BMI?
Body Mass Index (BMI) is a simple numerical value calculated from a person's weight and height. It was developed in the 1830s by Belgian mathematician Adolphe Quetelet and is widely used today as a screening tool to identify potential weight-related health issues in adults.
BMI is not a diagnostic tool — it doesn't directly measure body fat or health. A person with a high BMI might be very muscular rather than overweight. Always consult a healthcare provider for a full health assessment.
BMI Formula
Metric: BMI = weight(kg) ÷ height(m)²
Imperial: BMI = 703 × weight(lbs) ÷ height(in)²
For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75²) = 22.9, which falls in the Normal weight category.
Frequently Asked Questions
Is BMI accurate for everyone?
BMI has limitations. It can overestimate body fat in athletes and underestimate it in older adults who have lost muscle mass. It also does not account for fat distribution, which affects health risks. For a more complete picture, consider waist circumference or body fat percentage.
What is a healthy BMI for adults?
For most adults, a BMI between 18.5 and 24.9 is considered healthy. However, optimal BMI ranges may vary by age, sex, and ethnicity. Asian populations, for example, may face health risks at lower BMI values.
How do I lose weight to reach a healthy BMI?
A combination of a caloric deficit (eating fewer calories than you burn) and regular physical activity is the most evidence-based approach. A deficit of 500 calories per day typically leads to approximately 0.5 kg (1 lb) of weight loss per week.