Body mass index, or BMI, is an approximate measurement of your body fat as determined by your height and weight, according to the U.S. Department of Health and Human Services. Though your BMI measurement is only an estimate, it is helpful in determining whether you are underweight, normal weight, overweight or obese. Your BMI is another metric you can use when dieting or attempting to gain weight. Though several scales now include a BMI readout, you can determine your BMI by following a specific formula.
Step 1
Take off your shoes and measure your height using measuring tape or another measuring device. Convert your height to inches. For example, a person measuring 5 ft. 10 inches is 70 inches tall.
Step 2
Determine your weight by standing on a scale. To continue our example, the weight for the 70-inch person is 170 pounds.
Step 3
Multiply the height in inches by itself and then the weight by 703. In this example, you would use the formula 70 x 70 for height and 170 x 703 for weight. The answers in this example are 4,900 and 119,510.
Step 4
Divide the answer for the weight formula by the answer for the height formula to determine your body mass index. Finishing our example, the formula is 119,510 / 4,900. The answer is 24.3897959 for the body mass index, which is rounded to 24.4.
Step 5
The following guidelines determine if you are underweight, normal weight, overweight or obese. A BMI under 18.5 is considered underweight; 8.5 to 24.9 is normal weight; 25 to 29.9 is overweight; and above 30 is considered obese.
Tips and Warnings
- The BMI only provides an approximate determination of weight status. Individuals with different body builds, such as those with high muscle mass, may end up with an overweight result, which is incorrect. Only use the body mass index as a guideline.
Things You'll Need
- Tape measure or other measuring device
- Scale
- Calculator
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