## Children (aged 2 to 20)

BMI for age percentiles for boys 2 to 20 years of age.

BMI for age percentiles for girls 2 to 20 years of age.

BMI is used differently for children. It is calculated in the same way as for adults, but then compared to typical values for other children of the same age. Instead of comparison against fixed thresholds for underweight and overweight, the BMI is compared against the percentiles for children of the same sex and age.

A BMI that is less than the 5th percentile is considered underweight and above the 95th percentile is considered obese. Children with a BMI between the 85th and 95th percentile are considered to be overweight.

Recent studies in Britain have indicated that females between the ages 12 and 16 have a higher BMI than males of the same age by 1.0 kg/m2 on average.

# BMI Calculator

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## BMI formula

The BMI (Body Mass Index) in (kg/m2) is equal to the mass in kilograms (kg) divided by the square height in meters (m):

BMI(kg/m2) = mass(kg) / height2(m)

The BMI (Body Mass Index) in (kg/m2) is equal to the mass in pounds (lbs) divided by the square height in inches (in) times 703:

BMI(kg/m2) = mass(lb) / height2(in) × 703

### International variations

These recommended distinctions along the linear scale may vary from time to time and country to country, making global, longitudinal surveys problematic. People from different ethnic groups, populations, and descent have different associations between BMI, percentage of body fat, and health risks, with a higher risk of type 2 diabetes mellitus and atherosclerotic cardiovascular disease at BMIs lower than the WHO cut-off point for overweight, 25 kg/m2, although the cut-off for observed risk varies among different populations. The cut-off for observed risk varies based on populations and subpopulations both in Europe and Asia.

### United States

In 1998, the U.S. National Institutes of Health and the Centers for Disease Control and Prevention brought U.S. definitions in line with World Health Organization guidelines, lowering the normal/overweight cut-off from BMI 27.8 to BMI 25. This had the effect of redefining approximately 29 million Americans, previously healthy, to overweight.

This can partially explain the increase in the overweight diagnosis in the past 20 years, and the increase in sales of weight loss products during the same time. WHO also recommends lowering the normal/overweight threshold for South East Asian body types to around BMI 23, and expects further revisions to emerge from clinical studies of different body types.

The U.S. National Health and Nutrition Examination Survey of 2015-2016 showed that 71.6% of American men and women had BMIs over 25. Obesity—a BMI of 30 or more—was found in 39.8% of the US adults. A survey in 2007 showed 63% of Americans are overweight or obese, with 26% in the obese category (a BMI of 30 or more). As of 2014, 37.7% of adults in the United States were obese, categorized as 35.0% of men and 40.4% of women; class 3 obesity (BMI over 40) values were 7.7% for men and 9.9% for women.

 Body Mass Index values for males and females aged 20 and over, and selected percentiles by age: United States, 2011–2014. Age Percentile 5th 10th 15th 25th 50th 75th 85th 90th 95th Men BMI (kg/m2) 20 years and over (total) 20.7 22.2 23.0 24.6 27.7 31.6 34.0 36.1 39.8 20–29 years 19.3 20.5 21.2 22.5 25.5 30.5 33.1 35.1 39.2 30–39 years 21.1 22.4 23.3 24.8 27.5 31.9 35.1 36.5 39.3 40–49 years 21.9 23.4 24.3 25.7 28.5 31.9 34.4 36.5 40.0 50–59 years 21.6 22.7 23.6 25.4 28.3 32.0 34.0 35.2 40.3 60–69 years 21.6 22.7 23.6 25.3 28.0 32.4 35.3 36.9 41.2 70–79 years 21.5 23.2 23.9 25.4 27.8 30.9 33.1 34.9 38.9 80 years and over 20.0 21.5 22.5 24.1 26.3 29.0 31.1 32.3 33.8 Age Women BMI (kg/m2) 20 years and over (total) 19.6 21.0 22.0 23.6 27.7 33.2 36.5 39.3 43.3 20–29 years 18.6 19.8 20.7 21.9 25.6 31.8 36.0 38.9 42.0 30–39 years 19.8 21.1 22.0 23.3 27.6 33.1 36.6 40.0 44.7 40–49 years 20.0 21.5 22.5 23.7 28.1 33.4 37.0 39.6 44.5 50–59 years 19.9 21.5 22.2 24.5 28.6 34.4 38.3 40.7 45.2 60–69 years 20.0 21.7 23.0 24.5 28.9 33.4 36.1 38.7 41.8 70–79 years 20.5 22.1 22.9 24.6 28.3 33.4 36.5 39.1 42.9 80 years and over 19.3 20.4 21.3 23.3 26.1 29.7 30.9 32.8 35.2