BMI Formula
How are BMI Values Calculated?

Use can use the BMI formula to determine your body mass index (BMI) value as a means for assessing your basic level of health based solely on your height and weight. There are variations of the BMI formula depending on which units of measure you use, metric or English.

You should understand that the BMI index correlates with the amount of body fat but it does not directly measure body fat. As a result, some people, such as athletes like body builders or weight lifters that are very muscular, may have a BMI that identifies them as overweight even though they do not have excess body fat. However, for most of us, the information from this established index is a very valuable indicator of where we fall in the healthy weight to obese weight range.

The standard weight status categories associated with BMI ranges for adult men and women are shown in the following table:

Generally speaking, the BMI formula is a ratio of your weight to your height squared. The specific formula to use depends on whether you use the English or metric system of measurement.


Metric Calculation (kilograms/meters)
The formula for BMI using the metric system of measurement is the simplest of the variations. It is simply the ratio of your weight in kilograms to your height in meters squared as shown below:

   BMI = weight (kg) / height² (m²)


English Calculation (pounds/inches)
The formula for BMI using English units is essentially the same as the metric version except that you use pounds and inches squared and apply a multiplier of 703 as shown below:

   BMI = weight (lbs) / height² (in²) x 703


British Calculation (stones/meters)
For those of you in Britain that are still using the stone as measure of body weight, there yet another variation of this formula. This is similar to both the metric and English formulas but you use stones and meters squared and apply a multiplier of 6.35. (For everyone else, 1 stone is equal to 14lbs.) The formula using the British stone unit of measure is below:

   BMI = weight (stones) / height² (m²) x 6.35


Simply use the variation of the formula that applies to your preferred units of measure to calculate your BMI value. Note that you can also calculate your BMI value using a BMI calculator. The advantages of using a BMI calculator are that it is very simple and you can easily determine a goal weight for weight loss purposes. For example, you can enter your height and desired BMI value into the BMI calculator to determine what you would need to weigh to be at that BMI value.

You can also determine a healthy goal weight based on a desired BMI value using a BMI chart in much the same was as you would using a BMI calculator. Either of these methods is a great way to establish a healthy goal weight to strive for on your weight loss program!

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