To use a body mass index calculator, enter your height in inches, or feet and inches depending on the calculator, and your weight in pounds, explains Mayo Clinic. Many calculators have a metric version for centimeters and kilograms, respectively. This information is put into a formula that determines BMI, which in healthy people is between 18.5 and 24.9.
A simple BMI chart clearly indicates which group a person falls in, whether that be underweight, normal, overweight or obese, notes Mayo Clinic. The website offers tips to maintain or to get to a healthy BMI, such as a diet rich in nutrients and a lifestyle that includes exercise. Body mass index is generally a good estimate of body fat, which is itself a good estimate of health risks such as stroke, heart attack and diabetes.
There are pitfalls of using BMI as an individual measurement, according to Mayo Clinic. People with high muscle mass may have an overestimated BMI, while people with low muscle mass may have an underestimated one. Excessive abdominal fat can also cause an improperly estimated BMI. People of Asian descent may see their health risks increase at a BMI of 23, which is lower than the standard 25 for other populations.