BMI Calculator
| Category | BMI range (kg/m2) |
|---|---|
| Underweight | < 18.5 |
| Normal weight | 18.5 – 25 |
| Overweight | 25 – 30 |
| Obesity | > 30 |
Understanding Body Mass Index
Body Mass Index, commonly referred to as BMI, is a standard numerical calculation used to evaluate body weight relative to height. Established by the World Health Organization and used by health professionals worldwide, BMI serves as a general indicator of whether an individual falls within a healthy weight range.
How BMI is Calculated
BMI measures the ratio of an individual's weight in proportion to their height squared.
In metric units, the calculation is performed by dividing weight in kilograms by height in meters squared.
In United States customary units, weight in pounds is divided by height in inches squared, and the result is multiplied by seven hundred and three.
Adult Weight Categories
For adults aged twenty and older, BMI values are grouped into specific classifications defined by the World Health Organization:
- Severe Thinness: Less than 16.0
- Moderate Thinness: 16.0 to 16.9
- Mild Thinness: 17.0 to 18.4
- Normal Weight: 18.5 to 24.9
- Overweight: 25.0 to 29.9
- Obese Class 1: 30.0 to 34.9
- Obese Class 2: 35.0 to 39.9
- Obese Class 3: 40.0 or greater
Health Risks Related to BMI
Maintaining a BMI within the normal range helps minimize health risks associated with being underweight or overweight.
Carrying excess weight is linked to elevated blood pressure, high cholesterol, type two diabetes, coronary heart disease, stroke, sleep apnea, and joint issues like osteoarthritis.
Conversely, being significantly underweight presents risks such as malnutrition, vitamin deficiencies, weakened immunity, bone loss, and potential growth issues.
Limitations of the Measurement
While BMI is useful for general screening, it does not directly measure body fat or muscle distribution.
Because muscle density is greater than fat, athletic individuals with high muscle mass may be classified as overweight despite having low body fat.
Additionally, age and gender play a role, as women and older adults typically carry a higher proportion of body fat compared to younger men with the same BMI reading.
BMI calculations are meant to provide basic guidance and should be interpreted alongside professional medical evaluation.