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Body mass index (BMI)


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Charts and calculators
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Theory / Evidence
  • Body mass index (BMI) is a widely accepted measurement that has been correlated with risk of developing disease. Adult BMI is also related to child BMI and adiposity, but it is possible that the magnitude of this association dependson the relative fatness of children. It is unclear, however, whether certain disease precede increased BMI or vice versa. For instance, asthma development may be a point on the trajectory of chronic obesity disease or asthma may appear with obesity as a concurrent disorder.

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  • This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (

  1. Centers for Disease Control and Prevention (CDC). BMI Calculator. 16 May 2006.
  2. Centers for Disease Control and Prevention (CDC). Body Mass Index: About BMI for Adults. 16 may 2006.
  3. Centers for Disease Control and Prevention (CDC). Body Mass Index: About BMI for Children and Teens. 16 May 2006.
  4. Freedman DS, Khan LK, Serdula MK, et al. The relation of childhood BMI to adult adiposity: the Bogalusa Heart Study. Pediatrics. 2005 Jan;115(1):22-7.
  5. Freedman DS, Khan LK, Serdula MK, et al. The relation of menarcheal age to obesity in childhood and adulthood: the Bogalusa heart study. BMC Pediatr. 2003 Apr 30;3:3.
  6. Halls S, Hanson J. Body Mass Index Charts of Men. 16 May 2006.
  7. Stanley AH, Demissie K, Rhoads GG. Asthma development with obesity exposure: observations from the cohort of the National Health and Nutrition Evaluation Survey Epidemiologic Follow-up Study (NHEFS).J Asthma. 2005 Mar;42(2):97-9.

Charts and calculators
  • For adults, the accepted formula for calculating adult (20 years and older) BMI is:
  • English: BMI=703 x [Weight in pounds/(Height in inches)2]
  • Metric: BMI= [Weight in kilograms/(Height in meters)2]
  • Note: 2.2 lb=1kg
  • Body Surface Area = 0.20247 x Height(m)0.725 x Weight(kg)0.425
  • The formula for adult BMI can be used with children, although the results are interpreted differently. BMI charts showing percentiles are used with children 2-20 years of age. Related growth charts include head circumference-for-age (infants 0-36 months), weight-for-length percentiles (infants 0-36 months), stature-for-age (2-20 years) and weight-for-age (2-20 years).
  • Although there is general consensus that BMI for adults is associated with increased disease risk, there are differences in BMI for men and women, and older and younger adults. The graphs below show that older children's (boys) BMI increases up to age 20, (and keeps on increasing after that). This data came from the standard CDC growth charts. There is a gap between the children and adult data, because the data sources are different. The adult data (from the NHANES III survey) comes from data collected between 1988 and 1994, whereas the CDC body-mass-index-for-age charts are derived from a mix of data from new and older sources. A similar chart is provided for the women. The statement that over 50% of Americans are overweight relies on these graphs: the 50th percentile of men have a BMI of 25 or above, which is considered overweight according to most CDC charts. Similarly, 50% of American women over 30 also have a BMI that is considered overweight and at risk.

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    The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.

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