CDC BMI Calculator (Adult BMI)
Enter your height and weight using U.S. or metric units to estimate your Body Mass Index (BMI) and CDC weight category.
What is a CDC BMI calculator?
A CDC BMI calculator is a tool that estimates Body Mass Index using your height and weight. BMI is a screening measure used by the Centers for Disease Control and Prevention (CDC) to help identify whether an adult may be underweight, at a healthy weight, overweight, or in an obesity range.
It is important to remember that BMI is not a diagnosis. It is a fast way to flag possible risk, which can then be reviewed with other information such as blood pressure, blood sugar, cholesterol, waist size, physical activity, and family history.
How BMI is calculated
U.S. customary formula
BMI = (weight in pounds ÷ height in inches²) × 703
Metric formula
BMI = weight in kilograms ÷ height in meters²
The calculator above uses these exact formulas and then maps your result to CDC adult BMI categories.
CDC adult BMI categories (age 20 and older)
| Category | BMI Range |
|---|---|
| Underweight | Below 18.5 |
| Healthy Weight | 18.5 to 24.9 |
| Overweight | 25.0 to 29.9 |
| Obesity (Class 1) | 30.0 to 34.9 |
| Obesity (Class 2) | 35.0 to 39.9 |
| Obesity (Class 3) | 40.0 and above |
How to use this BMI tool effectively
- Choose the correct unit system before entering values.
- Use accurate measurements (without shoes for height, consistent scale for weight).
- Track trends over time rather than focusing on one reading.
- Use BMI with other health indicators, not by itself.
What your result means
If your BMI is outside the healthy range, that does not automatically mean you are unhealthy. It means you should look closer. A clinician may evaluate body composition, diet quality, activity patterns, sleep, stress, and metabolic markers before making recommendations.
If your BMI is in the healthy range, that is generally favorable, but it is still possible to have elevated health risks. Good preventive care includes regular movement, quality nutrition, strength training, and routine checkups.
Adults vs. children and teens
For adults, BMI ranges are fixed. For children and teens ages 2-19, CDC interpretation is different: it uses BMI-for-age percentile based on age and sex. A child with the same BMI number as an adult is not interpreted the same way.
If you are calculating BMI for a child or teen, use a CDC pediatric growth chart tool and discuss the result with a pediatric provider.
Limitations of BMI
BMI is useful at the population level, but it has known limitations for individual decision-making:
- It does not directly measure body fat.
- It cannot distinguish fat mass from muscle mass.
- It does not show fat distribution (for example, abdominal fat).
- It may misclassify some athletes, older adults, or people with unique body composition.
Practical next steps if your BMI is high
1) Focus on sustainable habits
Prioritize high-protein meals, high-fiber foods, water intake, and regular movement. Small daily improvements are more effective than short-term extremes.
2) Build strength and fitness
Resistance training 2-4 times per week can improve metabolic health, preserve lean mass, and support long-term weight management.
3) Monitor key health metrics
Track waist circumference, resting heart rate, blood pressure, and lab values with your clinician for a fuller picture of risk.
Frequently asked questions
Is BMI accurate?
It is accurate as a quick screening estimate. It is not a complete diagnostic tool for body composition or disease.
How often should I calculate BMI?
Monthly is usually enough for trend tracking. Weekly checks may be useful during active lifestyle changes, but daily fluctuations can be misleading.
What is a healthy BMI target?
For most adults, a BMI between 18.5 and 24.9 is considered healthy by CDC standards. Your ideal target may vary depending on your health history and provider guidance.
Medical note: This calculator is for educational use and screening only. It does not replace professional medical advice, diagnosis, or treatment.