Body mass index, or BMI, is the formula that doctors and other health care professionals use to determine the appropriate weight for your height. While the BMI can be an effective tool in identifying excess weight, other assessments may be needed to determine if excess weight poses a health risk, according to the Centers for Disease Control and Prevention. Calculating your BMI only takes a few minutes and requires basic math skills, including division and multiplication.
Step 1
Measure your height with a measuring tape. Write down your height on a piece of paper. The BMI formula requires you to input your height in inches.
Step 2
Weigh yourself and write your weight in pounds on the paper. Make sure that the scale you use is adjusted correctly and is set at zero before you step on the scale.
Step 3
Enter your weight in pounds into a calculator and multiply the number by 703.
Step 4
Divide the number displayed in the calculator's display window by your height in inches.
Step 5
Note the number resulting from the division function, and divide that number by your height in inches again. The number you see in the calculator display window is your BMI.
Step 6
Use your BMI number to determine if you are underweight, at a normal weight or overweight. If your BMI is lower than 18.5 you are underweight, while a BMI between 18.5 and 24.9 means you are at a healthy weight. If your BMI is between 25 and 29.9, you are overweight. A BMI of 30 to 39.9 indicates obesity, while a BMI over 40 indicates that you are morbidly obese.
Tips and Warnings
- While your BMI can be helpful in determining if you are overweight, other factors may also affect your weight designation. Body builders may have a higher BMI because muscle weighs more than fat, according to MedlinePlus. Elderly people may require a slightly higher BMI than younger people to protect against osteoporosis. Your BMI is just one tool your doctor uses to determine if you are at a healthy weight. Other considerations include your diet, sex, family history of medical diseases and any medical conditions you may have, such as high blood pressure. Your doctor considers these factors when deciding if a higher than normal BMI poses a health risk for you.
- Don't use the adult BMI formula for people under age 20. The Centers for Disease Control and Prevention reports that interpretation of the BMI is age- and sex-specific for children and teens, while the general BMI is interpreted using standard weight categories for both sexes in adults. A separate BMI calculator is used for children and teenagers.
Things You'll Need
- Measuring tape
- Paper
- Scale
- Calculator
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