Body Mass Index Calculator

 BMI For Adults
20 years old and older

Height: ft in
BMI Prime:~
Overweight %:~
Weight to lose:~
Time on Diet:~
Calories to Burn:~
Severely Underweight:~
Obese Class I:~
Obese Class II:~
Obese Class III:~
31 January, 2015
 BMI For Kids
Aged 2 to 20 years old

Birth date:
Height: ft in
Birth Date:~
97th percentile BMI:~
95th percentile BMI:~
90th percentile BMI:~
85th percentile BMI:~
75th percentile BMI:~
50th percentile BMI:~
25th percentile BMI:~
10th percentile BMI:~
5th percentile BMI:~
3rd percentile BMI:~
31 January, 2015
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.

CategoryBMI rangeBMI Prime
Severely underweightless than 16.5less than 0.66
Underweightfrom 16.5 to 18.4from 0.66 to 0.73
Normalfrom 18.5 to 24.9from 0.74 to 0.99
Overweightfrom 25 to 29.9from 1.0 to 1.19
Obese Class Ifrom 30 to 34.9from 1.2 to 1.39
Obese Class IIfrom 35 to 39.9from 1.4 to 1.59
Obese Class IIIover 40over 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
Please talk with your doctor if you have questions about your BMI.

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.

CategoryPercentile Range
ObeseEqual to or greater than the 95th percentile
Overweight85th to less than the 95th percentile
Healthy weight5th percentile to less than the 85th percentile
UnderweightLess 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.