How to Measure Your BMI

Your body mass index is a number that indicates body fat. You can calculate your BMI by using a formula that involves your height and weight. Use your BMI to help determine if you are underweight, normal weight, overweight or obese.

Step 1

Stand barefoot against a wall and look straight ahead. Place a ruler on top of your head so that it is parallel to the floor, with one end touching the wall. Mark the spot where the ruler touches the wall and use the measuring tape to measure the distance from the floor to the mark, in inches. This is your height.

Step 2

Remove your shoes and clothing, then step on a scale to find your weight. If you are using a public scale at a health club or doctor's office, wear light clothing such as a T-shirt and shorts.

Step 3

Divide your weight by your height in inches squared, then multiply by 703. For example if you are six feet tall and weigh 200 pounds, your BMI is 200 divided by 5,184 times 703, which equals 27.12.

Step 4

Compare your BMI to the categories. A BMI below 18.5 indicates you are underweight. A BM1 from 18.5 to 24.9 is normal. A BMI from 25.0 to 29.9 indicates you are overweight and 30.0 and above means you are obese.


  • You may need a friend to help you place the ruler on your head so that it is parallel to the floor.
  • Women tend to have more body fat than men with the same BMI and older people tend to have more body fat than younger adults with the same BMI. Athletes might also have a high BMI because they have larger muscles, not extra fat.