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Body Mass Index BMI - Calculator
Height - Weight System to Determine Normal Weight, Overweight and Obesity
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Weight Assessment & Weight Related Risk Measurement System for Optimum Weight Management

Body Mass Index - BMI (See Below for BMI Calculator)

What is Body Mass Index?

Body Mass Index (BMI) is a height/weight formula used by health and weight professionals around the world to assess a person's body weight. From your body mass index number you can see if you are underweight, normal weight, overweight or obese.

BMI is a good gauge of the average person's weight status, including their total body fat, and an accurate predictor of health risks that flow from overweight and obesity. In short, the higher your BMI, the greater the risk of developing additional health problems.

BMI Notes
"Overweight" is defined as an excess amount of body weight, including fat, muscle, bone and water. "Obesity" is defined as an excess amount of body fat. Thus an athlete or muscular person may be overweight without being obese.

Body Mass Index Formula

BMI equals a person's weight in kilograms divided by height in meters squared. Or: BMI=kg/m2.

How to Calculate Your BMI

Follow instructions below, or else simply click:

American Units:

1. Measure and record your weight in pounds
2. Measure and record your height in inches
3. Body Mass Index =
Weight [in pounds] X 704.5 divided by (Height [in inches] X Height [in inches])

BMI Example

You are 5 feet 4 inches (64 inches)
Your weight is 175 pounds
Your BMI is: (175 X 704.5) divided by (64 X 64) = 30

Metric Units:

1. Measure and record your weight in kilograms
2. Measure and record your height in meters
3. Body Mass Index = weight in kilograms divided by height squared in meters

Or: BMI = Weight [in kilos] divided by (Height [in meters] X Height [in meters])

BMI Example

You are 1.57 meters tall (5 feet 2 inches)
Your weight is 65 kilos (143 pounds)
Your BMI is: 65 divided by (1.57 X 1.57) = 26

Body Mass Index Results - Healthy Weight - Overweight

In June 1998, the US Federal Government announced guidelines which create a new definition of a healthy weight - a BMI of 20-24.99. So now a BMI of 25 to 29.99 is considered overweight.

Body Mass Index - Underweight, Normal Weight, Overweight, Obese

BMI conclusions vary slightly according to gender. Here is a general summary of weight-status based on BMI.

Under 20 (19 for women) = Underweight
Between 20 and 24.99 = Normal Weight
Between 25 and 29.99 = Overweight
Between 30 and 34.99 = Obese Class 1
Between 35 and 39.99 = Obese Class 2
40 and above = Extreme (Morbid) Obesity

Body Mass Index and Health Risks

BMI is important because if your BMI is high, you are at greater risk of developing certain illnesses. By being aware of your BMI and changing it, you reduce your risk considerably.

Some of the diseases/illnesses that can be caused by a heightened BMI:

  • Hypertension
  • Cardiovascular Disease
  • Dyslipidemia
  • Adult-Onset Diabetes (Type II)
  • Sleep Apnea
  • Osteoarthritis
  • Female Infertility
  • Idiopathic intracranial hypertension
  • Lower extremity venous stasis disease
  • Gastro esophageal reflux
  • Urinary stress incontinence

Disease Risk According to Body Mass Index (BMI)

Body Mass Index (BMI) Disease Risk

BMI of < 20.00 - Risk = Moderate to Very High
20.00 to 21.99 - Risk = Low
22.00 to 24.99 - Risk = Very Low
25.00 to 29.99 - Risk = Low
30.00 to 34.99 - Risk = Moderate
35.00 to 39.99 - Risk = High
BMI of > 40.00 - Risk = Very High

Body Mass Index - Drawbacks

Using BMI to predict overweight has its limitations. For example, one variable BMI fails to consider is lean body mass. Thus it is possible for a healthy, muscular individual with very low body fat to be classified obese using the BMI formula. So if you are a trained athlete, your weight based on your measured percent body fat would be a better indicator of what you should weigh.

Also, BMI doesn't take frame size into account, so people with stockier builds may be considered overweight even if they don't have a lot of body fat. One final problem with BMI is that different authorities translate the information differently - they disagree slightly on what BMI range constitutes underweight, normal weight, overweight and obesity - which can cause some confusion in the results.

BMI Drawbacks - A Summary

BMI is not a good predictor of overweight for:

  • Children and teens, because BMI ranges are based on adult heights.
  • Competitive athletes and bodybuilders, because heavier muscle weight may skew the results.
  • Pregnant or nursing women, because they need more fat reserves than usual.
  • People over 65, because even BMI values of 29 do not appear to be unhealthy at this age, and may even be a useful energy reserve in case of illness.

Enhancing Your Body Mass Index Result

As outlined above, BMI is not a perfect indication of total body fat or lean body mass. One way of enhancing BMI results is to measure your waist circumference. Even this is not an absolute guide to your percentage or total of body fat, but it does provide information on the location of your body fat. Although total body fat is still more important regarding weight-related health risks, location of body fat is also thought to be a highly relevant health consideration.

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