Less than half of the adults in the United States have a healthy BMI. For adults, an ideal range is between 18.5 and 24.9; a person with a BMI over 24.9 is considered overweight, and a person with a BMI under 18.5 is considered underweight. For children, a BMI between the 5th and 85th percentiles is considered healthy.
Body mass index (BMI for short) is a tool that can be used to indirectly measure body fatness. Because the calculation requires only height and weight, it is inexpensive and easy for healthcare providers and the general public to use as a method of screening for weight categories that may lead to health problems.
(Click BMI Calculator to find your BMI.)
Although the BMI formula for adults and children is the same, the way the results are interpreted differ. Therefore, what is considered a healthy BMI also differs.
For adults, an ideal BMI is between 18.5 and 24.9. A person with a BMI over 24.9 is considered overweight. A person with a BMI under 18.5 is considered underweight.
For children, a healthy BMI is between the 5th and 85th percentiles.
This test is valid for both men and women, but it does have some limits. When using BMI to calculate body fatness, keep in mind that it may:
- Underestimate body fat in older people and others who have lost muscle mass
- Overestimate body fat in athletes and others who have a muscular build.
Therefore, it is possible for a person to be completely healthy but have an "unhealthy BMI." To account for these limitations, healthcare providers consider other factors when assessing the health risk for certain medical conditions.
(Click BMI and Weight for more information on other factors healthcare providers consider when determining risk for certain medical conditions related to weight.)