 Convert your weight in pounds to your weight in kilograms by dividing your weight in pounds by 2.2.
 Convert your height in inches to your height in meters by multiplying your height in inches  not feet  by 0.0254. (If you are 5 feet tall, your height is 60 inches, or 1.52 meters. If you are 6 feet tall, your height is 72 inches, or 1.83 meters.)
 Square your height in meters (that is, multiply your height in meters by itself).
 Divide your weight in kilograms by the number you obtained in the previous step.
Body Mass Index (BMI)
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18 AnswersDr. Michael Roizen, MD , Internal Medicine, answeredIf you want to calculate your BMI, the formula for doing so is relatively easy:

4 AnswersDefinitely. There is a direct relationship between a high BMI and a higher risk of early death, as well as a correlation with certain diseases: diabetes, heart disease, stroke (as a result of increasing the rates of high blood pressure, high cholesterol, type2 diabetes), even arthritis and certain cancers.
Virtually every organ system in the body is adversely affected by obesity. Moreover, obesity, especially if severe, decreases life expectancy and healthrelated quality of life. Distribution of the excess fat is an important modifier of health risk, though. Excess abdominal/ visceral fat increases the risk, while lower body excess fat is safer. 
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The formula for BMI is in metric units: kilograms per metersquared. If you don’t want to convert your height and weight to metric, there are multiple calculators on the web to use (search for “BMI calculator), or you can use the following nonmetric formula: 704 times (X) pounds of body weight, divided by height in inchessquared.
The same formula is used for adult men and women of any age, but children are graphed on a different chart, and BMI is expressed as a percentile for that age or height.

3 AnswersNational Academy of Sports Medicine answeredUnfortunately, BMI (body mass index) is not a very good indication of fat mass or muscle mass. BMI is heighttoweight ratio that is calculated by dividing your weight in kilograms by your height in meters squared. Due to this, BMI does not differentiate between fat and muscle because that is not what it was intended to do. BMI is meant to be a simple calculations to be an indicator of obesity. If someone has a BMI of over 35, they are at severe risk of obesityrelated diseases. When calculating the BMI of someone with large amounts of muscle mass, the results becomes inaccurate because it will classify them obese. A better way to track body fat is with skin fold calipers. The calipers estimate the percentage of fat mass that is in the body. You can multiply this percentage by your total body weight to determine the number of pounds of fat you have in your body.

3 AnswersDebra Fulghum Bruce PhD , Healthcare, answeredHere’s a simple formula to tell if you are an apple or pear: Break out your measuring tape, measure your waist in inches at its narrowest point, and then divide by your hip measurement in inches at the widest point. For women the apple/pear score should not exceed 0.80. For men the score should not exceed 0.95

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The normal range of BMI is from 18.5 to 25. Of course, genetics and luck play a large role in health as well. There are many obese people who will stay healthy, and thin people who will not. Staying physically fit seems to improve health, even among people who are obese.

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A BMI of less than 18.5 is underweight, 18.524.9 is normal weight, 2529.9 is overweight, 3039.9 is obese, and 40+ is severely obese (usually 100+ lbs over ideal weight).
Among healthy US adults, fewer than 2% are underweight, about 30% are normal weight, a third are overweight, and another third obese. Thus, you are in the minority currently if your weight is in the normal range!

32 AnswersDr. Michael Roizen, MD , Internal Medicine, answeredThe customary way to calculate your ideal weight is to determine your body mass index (BMI) or your weighttoheight ratio. Although The BMI is one of the best tools we have for assessing whether or not a person weighs too much it is not very useful in young body builders or athletes. The BMI is useful for the majority of us as it accounts for variances in body size, giving a standard for evaluating people at a range of heights. (BMI does not provide the best possible measure of body fat, for most people BMI provides a good general estimate and can easily be calculated at home.)

7 AnswersNational Academy of Sports Medicine answeredBody Mass index is a weight to height ratio that is used to classify individuals as underweight, normal, overweight, or obese. This also helps to estimate an individual’s risk of health problems, based on excess weight.
While this is a quick and easy tool, it does have some limitations. BMI does not take body composition into account (whether your weight is made up of more muscle or fat). Therefore, a very muscular individual might be heavier than what is normal for their height group, and according to this calculation they could be considered overweight or obese. Having more lean muscle is certainly advantageous to your health, so this would be one instance in which a high BMI number would actually be okay. 
10 AnswersNational Academy of Sports Medicine answeredBody mass index is an easy assessment that can be performed in order to estimate disease risk. However, this should not be used in place of annual physical exams and other health tests.