# What Is BMI How Is BMI Calculated

I was really surprised to find out that BMI was created in the 1800’s as it is only in the last couple of years that I have heard of it.  All of a sudden everyone seems to be relying on BMI to tell them whether they are overweight or not and as a guide in their weight loss journey.  BMI can’t actually help you lose weight, it is simply a measure of your weight in relation to your height.  Your BMI result will indicate whether you are in the right weight range for your height or whether you are under or over weight.

BMI is shortened for Body Mass Index.  It is a tool that measures body mass and has been around for 200 years.  BMI was created by Adolphe Quetelet and is sometimes referred to as the Quetelet index.  Adolphe Quetelet developed the BMI formula while working on social physics and it is still used today, 200 years later, with very little variation from it’s original form.

So we know that BMI measures body mass, but what does that actually mean?  Well, it doesn’t measure a person’s body fat, but rather it compares a person’s height to their weight to determine if they are in a healthy weight range for their height.  It is a tool that is widely used by doctors, fitness trainers and even insurance companies to determine whether a person is overweight or obese.  The BMI formula is not without it’s flaws and in some cases is not 100% accurate, but it is still the preferred tool used in the medical community.

Let’s take a look at the formula used to calculate a persons BMI.  First you take your height in meters and square it – you times it by itself.  Then you divide your weight in kilograms by the answer to your height squared.  For example, if a person is 1.5 meters tall you would times 1.5 by 1.5 which will give you 2.25.  If that person weights 54 kilograms you would then divide 54 by 2.25 which gives you an answer of 24 and this is your BMI.

What does that mean?

Your weight status is worked out by where it lies on the BMI chart.  A normal weight range has a BMI of between 18.5 and 24.9.  If your BMI is below 18.5 then this indicates that you are underweight.  Likewise if your BMI is in the range of 25 to 29.9 this indicates that you are overweight.  A BMI of 30 or more indicates obesity.  Using our example above of a person 1.5 meters tall and weighing 54 kilograms, they fall within the normal weight range at a BMI of 24.

I mentioned earlier that BMI figures are not accurate 100% of the time and this is mainly so with people that are extremely muscular.  The BMI formula doesn’t distinguish between muscle and fat and because muscle is much heavier than fat then the result is not accurate.  A body builder for example would have a large muscle mass and so his weight would be quite high when compared to his height.  This would give him a high BMI, although in actual fact he may not have an ounce of fat on his body.  For the majority of people though, BMI will give an accurate indication of whether you have a good weight for your height or not.

Next time you hear someone talking about BMI you will know exactly what they are talking about and could even tell them how it is calculated.  BMI is simply a comparison of a person’s weight to their height to determine whether they are in a healthy weight range.