BMI Calulator
What is BMI
Simply put, BMI, or body mass index is a simple way of assessing body fatness for most people. It does not measure body fat directly, but estimates it using height and weight measurements. Despite it’s simplicity, research has shown a strong correlation between BMI and other more precise, but more complicated body fat measurement techniques.
How is BMI Interpreted?
The BMI, for adults, is classified into four ranges: underweight, normal, overweight and obese. Those classifications and the ranges assoicated with them are shown below. BMI for children and teens (those under age 20), are interpreted differently. See below.
| BMI | BMI Classification |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal |
| 25.0 – 29.9 | Overweight |
| 30.0 or more | Obese |
Note: The WHO BMI Classification scheme is slightly more elaborate. It splits up the classifications into subclasses such as pre obese, moderate thinness, obese class I etc. A table show these classes can be found on the WHO’s BMI Classification page
BMI Variations
The correlation of BMI to actual body fatness is strong, but does vary according to age, sex and race. For example if both a man and a woman have the same BMI, it is likely that the female has a higher percentage body fat. Athelete may have a higher BMI due to above average muscle mass. That said, the correltion is strong for the general population and BMI does serve as the easiest, most commonly uses screening technique for obesity.
BMI for Children and Teens
BMI is used for children and teens as well. Because BMI varies based on age and sex a separate calculator must be used to attain the body mass index for those under 20. Here is a link to the "CDC’s Child and Teen BMI Calulator:http://apps.nccd.cdc.gov/dnpabmi/
How is BMI Calculated?
BMI is simply the ratio of weight to height squared. The standard BMI is based on weight in kilograms height in centimeters so in convetional terms the formula is:
BMI = ((weight in pounds) * 703) / [ (height in inches) * (height in inches)]
For example a 6 foot man weighing 175lbs. will have a BMI of 23.7
6 ft. = 72 inches
175*703 = 123025
72*72 = 5184
123,025/5184 = 23.73
For More Information
The CDC has a very good section of their website on healthy weight. This includes sections on losing weight, tips for parents, and the health effects of being overweight.
The WHO has a global strategy on diet, physical activity and health as well a global database on body mass index.
