How To Calculate BMI (Body Mass Index)

Body Mass Index, sometimes knows as Quetelet Index, is a measure of body fat based on a person’s height and mass(weight). Despite it only becoming more well known in recent years, this method of measuring body fat has been around since the 1800s. It was devised by the Belgian polymath, Adolphe Quetelet.It should be noted however that this method is not 100% accurate. This is understandable as the only measurements used are height and mass. So for example with a body builder, it may calculate the BMI as being obese, when in actual fact the bodybuilder is fit and healthy!So how do we calculate BMI?

Now you can calculate you’re BMI in metric or imperial units. So for metric, it would be you’re mass in kg and height in metres. You would then calculate you’re BMI with the following formula:

BMI= mass(kg)

With imperial you have a few choices with what units of measurements you want to choose. Depending on which units you choose, there is a specific way of calculating the BMI.

If you are going to measure mass in lbs and height in inches then the forumla will be:

BMI= mass(lb)
           height(m)²       Multiplythe answer by 703

If you are going to measure mass in lbs and height in ft then the formula will be:

BMI= mass(lb)
           height(ft)²       Multiply the answer by 4.88

If you are going to measure the mass in stones and the height in inches then the formula will be:

BMI= mass(st)
           height(in)²       Multiply the answer by 9840

Ok so you now have calculated you’re BMI, so where do you stand? The following chart is a rough guide of where you fall:


Underweight         Below 18.5

Normal                  18.5-24.9

Overweight           25.0-29.9

Obesity                 30.0 and above

You can also use the following chart to see where you fall:

So there you go, that’s how you can calculate you’re BMI.

Thanks for reading, hope it helped!

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