For adults, an ideal BMI is within the range of 18.5 and 24.9. Children and teenagers should be between the 5th and 85th percentile. However, athletes and people with muscular builds often have high BMI numbers. Recent studies show that less than half of U.S. adults have an ideal body mass index and approximately 15 percent of children and adolescents are overweight.
Body mass index (or BMI) is a tool that can be used to indirectly measure the level of body fatness in an individual. Because the calculation requires only two pieces of information, height and weight, it is an inexpensive and easy screening method for weight categories that may lead to health problems.
(Click BMI Calculator to determine your body mass index.)
Although the BMI formula for adults and children is the same, the way that the results are interpreted differs. Therefore, what is considered an ideal 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, and a person with a BMI under 18.5 is considered underweight.
For children, an ideal number is between the 5th and 85th percentile.
The BMI score is valid for both men and women, but it does have some limits. When used to calculate body fatness, it may:
- Overestimate body fat in athletes and others who have a muscular build
- Underestimate body fat in older persons and others who have lost muscle mass.
Therefore, it is possible for a person to be completely healthy but have an "unhealthy BMI." This is why healthcare providers consider other factors besides this 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.)