Body Mass Index Calculator

 BMI For Adults20 years old and older lbs ft in cm
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 BMI For KidsAged 2 to 20 years old Female Male lbs ft in cm
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The Body Mass Index (BMI) is a statistical measure of body weight based on a person's weight and height. Though it does not actually measure the percentage of body fat, it is used to estimate a healthy body weight based on a person's height.

Due to its ease of measurement and calculation, it is the most widely used diagnostic tool to identify weight problems within a population, usually whether individuals are underweight, overweight or obese. It was invented between 1830 and 1850 by the Belgian polymath Adolphe Quetelet during the course of developing "social physics".

Body Mass Index is defined as the individual's body weight divided by the square of his or her height: BMI = Mass(kg) / (height(m))²

BMI is frequently used to assess how much an individual's body weight departs from what is normal or desirable for a person of his or her height. The weight excess or deficiency may, in part, be accounted for by body fat although other factors such as muscularity also affect BMI significantly. The World Health Organization regard a BMI of less than 18.5 as underweight and may indicate malnutrition, an eating disorder, or other health problems, while a BMI greater than 25 is considered overweight and above 30 is considered obese. These ranges of BMI values are valid only as statistical categories when applied to adults, and do not predict health.

Category BMI range BMI Prime Severely underweight less than 16.5 less than 0.66 Underweight from 16.5 to 18.4 from 0.66 to 0.73 Normal from 18.5 to 24.9 from 0.74 to 0.99 Overweight from 25 to 29.9 from 1.0 to 1.19 Obese Class I from 30 to 34.9 from 1.2 to 1.39 Obese Class II from 35 to 39.9 from 1.4 to 1.59 Obese Class III over 40 over 1.6

For most people, BMI provides a reasonable estimate of body fat. Excess body fat is related to serious health conditions. Its biggest weakness is that it doesn't consider individual factors such as bone or muscle mass. BMI may:
• Underestimate body fat for older adults or other people with low muscle mass
• Overestimate body fat for people who are very muscular and physically fit
• Inadequately evaluate health risks of people with excess abdominal fat

The Body Mass Index (BMI) is a number calculated from a child's weight and height. BMI is a reliable indicator of body fatness for most children and teens. 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.

For children and teens, BMI is age- and sex-specific and is often referred to as BMI-for-age.

What is a BMI percentile?
After BMI is calculated for children and teens, the BMI number is plotted on the CDC BMI-for-age growth charts (for either girls or boys) to obtain a percentile ranking. Percentiles are the most commonly used indicator to assess the size and growth patterns of individual children in the United States. The percentile indicates the relative position of the child's BMI number among children of the same sex and age. The growth charts show the weight status categories used with children and teens (underweight, healthy weight, overweight, and obese).

BMI-for-age weight status categories and the corresponding percentiles are shown in the following table.

Category Percentile Range Obese Equal to or greater than the 95th percentile Overweight 85th to less than the 95th percentile Healthy weight 5th percentile to less than the 85th percentile Underweight Less than the 5th percentile

How is BMI used with children and teens?
BMI is used as a screening tool to identify possible weight problems for children. CDC and the American Academy of Pediatrics (AAP) recommend the use of BMI to screen for overweight and obesity in children beginning at 2 years old.

For children, BMI is used to screen for obesity, overweight, healthy weight, or underweight. However, BMI is not a diagnostic tool. For example, a child may have a high BMI for age and sex, but to determine if excess fat is a problem, a health care 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.