How is body mass index calculated?

Body Mass Index or BMI is a measurement that helps determine your ideal, optimum weight range based on your height. However, is it actually useful to monitor my BMI? and if so, how is body mass index calculated?

The idea behind body mass index is that the frame of each person varies making it difficult to give a specific, ideal weight for an individual’s height. It is far better to give a numeric range that a majority of the population should fall within. It should be noted that a runners physique will naturally vary to that of a muscular weight lifter. As the amount of muscle can significantly vary ones weight, BMI may not be an accurate measurement for athletes or those who are very muscular. BMI may also not be accurate for the very young, very old and women who are pregnant or breast feeding.

BMI is an important measurement because medical research has suggested that keeping your body mass index in the ideal range will lead to the best health and result in a lowered risk of some cancers, heart disease, osteoporosis and a number of other health issues. However, an ideal BMI does not indicate a healthy lifestyle and you should make every effort to get regular exercise and eat a well-balanced diet.

Body Mass Index Chart

How is body mass index calculated?

Simply follow these three easy steps to calculate your body mass index. Don’t be scared the maths isn’t too complicated!

1. Measure your height in metres. Multiply this height by itself. For example, I am 1.83m tall, so I calculated: 1.83 x 1.83 = 3.35
2. Check your weight in kilograms. For example, my weight is 70Kg.
3. Now, simply divide your weight by your height squared. In my case, I calculate: 70 divided by 3.35 = 20.9

My BMI is 20.9, which puts me inside the ideal range. So now you know how your body mass index is calculated see where you are in the following BMI chart:

BMI Range

Weight

0 – 18.5
Underweight
18.5 – 25
Ideal
25 – 30
Overweight
30 – 40
Obese – lose weight
40+
Very obese – lose weight now

Try the following methods as well as they may give you a better weight indicator than just the body mass index by itself.

Waist Measurement:

BMI does not take into account where you are holding any excess weight.  If you hold the weight around your midriff (apple shaped) then you are at a higher risk of diabetes and heart disease than if the weight is spread more towards your hips and buttocks (pear shaped). A waist circumference of over 37 inches for men or 32 inches for women indicates an increased risk. A waist circumference of over 40 inches for men and 35 inches for women is even more worrying.

Waist-Hip Ratio:

Once again this method looks at where you hold the weight. Are you an apple or pear? This is important because weight around your midriff could indicate a heightened risk of heart disease. Firstly, measure the distance around your hips (widest point around your hips and buttocks). Next, measure the circumference around your belly button (or slightly above at the widest point). Now divide the waist measurement by the hip measurement. For example, if your waist measurement is 32 inches and your hip is 37 inches then your ratio is: 32 / 37 = 0.86. A value of over 1.0 for men or 0.8 for women indicates that you urgently need to lose weight.

You should now know how body mass index is calculated. What methods do you use to make sure your weight is in control?

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