CDC Body Mass Index (BMI) Calculator
Use this calculator to estimate your Body Mass Index (BMI) based on your weight and height. BMI is a screening tool for weight categories that may lead to health problems.
Understanding Your Body Mass Index (BMI)
The Body Mass Index (BMI) is a simple numerical measure that is commonly used to classify whether an individual's weight is healthy in relation to their height. Developed in the 19th century by Adolphe Quetelet, it has become a widely accepted screening tool for potential weight-related health risks by organizations like the Centers for Disease Control and Prevention (CDC).
How is BMI Calculated?
The BMI calculation uses a straightforward formula that takes into account an individual's weight and height. For adults, the formula is:
BMI = (weight in pounds / (height in inches)2) * 703
This formula converts weight from pounds to kilograms and height from inches to meters, then applies the standard metric BMI formula (weight in kg / (height in m)2). The result is a single number that falls into one of several weight categories.
BMI Categories According to CDC
The CDC defines BMI categories for adults as follows:
- Underweight: BMI less than 18.5
- Normal or Healthy Weight: BMI between 18.5 and 24.9
- Overweight: BMI between 25.0 and 29.9
- Obesity: BMI of 30.0 or greater
It's important to note that these categories are general guidelines. For children and teens, BMI is calculated using the same formula but is interpreted differently, using age- and sex-specific percentile curves.
Why is BMI Useful?
BMI serves as an inexpensive and easy-to-perform screening method for weight categories that may lead to health problems. A high BMI can be an indicator of high body fatness, which can increase the risk of various health conditions, including heart disease, stroke, type 2 diabetes, certain cancers, and high blood pressure. Conversely, a very low BMI can also indicate health risks, such as malnutrition or weakened immune function.
Limitations of BMI
While BMI is a useful screening tool, it has limitations:
- Does not distinguish between fat and muscle: Athletes or very muscular individuals may have a high BMI but very little body fat.
- Age, sex, and ethnicity differences: BMI may not accurately reflect body fatness in all populations. For example, older adults may have less muscle mass, and some ethnic groups may have different body compositions.
- Distribution of fat: BMI doesn't account for where fat is stored. Abdominal fat (around the waist) is considered more dangerous than fat stored in other areas.
Therefore, BMI should be used as a screening tool and not as a definitive diagnostic measure. A healthcare provider can perform further assessments, such as skinfold thickness measurements, waist circumference, and evaluations of diet and physical activity, to determine if a person's weight poses a health risk.