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According to the CDC, Body Mass Index (BMI) is a number calculated from a person’s weight and height. BMI is a reliable indicator of body fat for people. BMI does not measure body fat directly, but research has shown that BMI correlates to direct measures of body fat, such as underwater weighing and dual energy X-ray absorptiometry (DXA). BMI can be considered an alternative for direct measures of body fat. Additionally, BMI is an inexpensive and easy-to-perform method of screening for weight categories that may lead to health problems. |
BMI is used as a screening tool to identify possible weight problems for adults. However, BMI is not a diagnostic tool. For example, a person may have a high BMI. However, to determine if excess weight is a health risk, a healthcare provider would need to perform further assessments. These assessments might include skinfold thickness measurements, evaluations of diet, physical activity, family history, and other appropriate health screenings.
How to Calculate Your BMI
BMI is calculated the same way for both adults and children. You can use the CDC's BMI Calculater that is based on the following formulas:
| Measurement Units |
Formula and Calculation |
| Kilograms and meters (or centimeters) |
Formula: weight (kg) / [height (m)]2 With the metric system, the formula for BMI is weight in kilograms divided by height in meters squared. Since height is commonly measured in centimeters, divide height in centimeters by 100 to obtain height in meters.
Example: Weight = 68 kg, Height = 165 cm (1.65 m)
Calculation: 68 ÷ (1.65)2 = 24.98
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| Pounds and inches |
Formula: weight (lb) / [height (in)]2 x 703 Calculate BMI by dividing weight in pounds (lbs) by height in inches (in) squared and multiplying by a conversion factor of 703.
Example: Weight = 150 lbs, Height = 5’5” (65")
Calculation: [150 ÷ (65)2] x 703 = 24.96
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Interpretation of BMI for adults
For adults 20 years old and older, BMI is interpreted using standard weight status categories that are the same for all ages and for both men and women. For children and teens, on the other hand, the interpretation of BMI is both age- and sex-specific. For more information about interpretation for children and teens, visit Child and Teen BMI Calculator
| BMI |
Weight Status |
| Below 18.5 |
Underweight |
| 18.5 - 24.9 |
Normal |
| 25.0 - 29.9 |
Overweight |
| 30.00 and Above |
Obese |
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