Body Mass Index

The Body Mass Index, or BMI is a popular calculation which uses your height and weight to attempt to estimate your percentage of body fat. The result can tell you whether you’re underweight, normal, overweight or obese.

Thanks to its simplicity and speed, it’s a calculation that’s very popular within the medical profession. It’s also a relatively easy way to notice those possible weight issues, and also detect if you’re at an increased risk of suffering certain chronic diseases such as heart disease, high blood pressure, type 2 diabetes, gallstones, respiratory issues, certain cancers, and metabolic syndrome.

Considering that we have a global population that’s becoming increasingly overweight or obese, calculating your BMI would seem to be a really smart move.

So in this short article, we’re going to give you a rundown of what you need to know about calculating your BMI. We’ll explain how to calculate your own body mass index, we’ll explain what the number actually means, and then we’ll help you make sense of what is happening when the result isn’t quite what you expect.

How to calculate your BMI

First up, let’s calculate your BMI. You can quickly do this using the following formula:

US BMI Formula

Formula: weight (lb) / [height (in)]2 x 703

  • Let’s say you weigh 155 lb. and your height is 5ft 11 inches.
  • First we need to find your height in inches. There are 12 inches in a foot so you measure 71 inches tall.
  • Then we need to find your height squared. In this case it’s 71 x 71= 5041
  • Then we need to divide your weight by this number. So we calculate 155/5041= 0.03
  • Finally we need to multiply 0.03 x 703. This gives you a BMI of 21.09

What does your BMI mean?

Once you’ve worked out what your body mass index is, it’s time to find out what it actually means. Here’s a quick chart:

BMI categories

  • Underweight = BMI less than 18.5
  • Normal weight = BMI between 18.5 and 24.9
  • Overweight = BMI between 25 and 29.9
  • Obesity = BMI of 30 or greater

‘My BMI says I’m overweight, but I’m not…

Don’t worry if your BMI calculation tells you that you’re overweight or unhealthy when you’re pretty sure that you’re not, especially if you’re not the ‘average Joe.’

There are many factors which can influence your BMI result, and they don’t necessarily mean you need to go on a strict diet!

Factors like your activity level, your health, your age, ethnicity, gender and most important body composition can all influence your BMI result. For example a person with high muscle mass and very low body fat (like a bodybuilder) will be still in the overweight or obese category.

So, is the BMI measurement still useful?

According to the World Health Organization, a BMI measurement is still a useful tool to be used in assessing a person’s weight and health, but it’s important to remember that it is merely an estimate.

It’s best used alongside other solid scientific methods such as such as waist circumference, hip measurement or even better a skinfold measurement

To conclude, we believe the body mass index can be a useful tool to use as an indication of the health ONLY for sedentary people that don’t have high amount of muscle mass. If you’re worried about your weight or your health, it’s always best to contact a doctor, accredited dietician or a certified personal trainer for specific assessment and guidance.