Body mass index, or BMI, is one way to look at whether a person is at a healthy weight. BMI is a number based on height and weight. It can be used to place a person in categories ranging from underweight to obese.
But BMI doesn’t work well for everybody. There are other things to think about when deciding how much someone should weigh. If you have a BMI outside the normal range, your health care provider might also look at skinfold thickness (a measure of body fat), waist size, evaluations of your diet and family health problems, blood sugar levels, and other factors to find out if your weight might pose a health risk. To learn more about BMI and how extra body weight can affect your risk of cancer, see Body Weight and Cancer Risk.
Enter your height and weight below to find your body mass index (BMI).
| BMI | Condition |
|---|---|
| Below 18.5 | Underweight |
| 18.5-24.9 | Normal weight |
| 25-29.9 | Overweight |
| 30 and higher | Obese |
If you are overweight or obese, even a small weight loss (10% of your current weight) can lower your risk of several diseases. People who are overweight or obese have a greater chance of developing several types of cancer—including colorectal cancer and breast cancer (for women past menopause)—as well as high blood pressure, high blood cholesterol or other lipid disorders, diabetes, heart disease, and stroke.
Being very underweight – especially if you’ve had rapid or unintentional weight loss – can also be a sign of health problems.