Online calculators that determine body mass index, or BMI, are available on reputable websites that include the Centers For Disease Control and Prevention and the National Heart, Lung, and Blood Institute. BMI calculations express a relationship between a person's height and weight.
BMI calculations represent the amount of body fat a person has and his level of risk for a variety of chronic diseases. BMI alone does not accurately gauge risk factors or the overall health of an individual, and further health screening by a health care professional is necessary.
BMI has four ranges, including underweight, healthy weight, overweight and obese, according to the Centers For Disease Control and Prevention. A BMI between 18.5 and 24.9 is a healthy weight range. If a BMI falls below 18.5, a person is underweight. An overweight person has a BMI of between 25 and 29.9, and a BMI of 30 or higher indicates obesity.
Although BMI calculations may be applicable for most adult men and women, there are some limitations, according to the National Heart, Lung and Blood Institute. The calculation may overestimate the body fat in those with a muscular build, such as bodybuilders and other athletes. Additionally, it may underestimate body fat in those who have lost a significant amount of muscle mass, such as elderly people.