Beginners Guide to Body Mass Index

BMI or body mass index is a way of judging someone’s weight to height ratio. It is basically a single number that shows how heavy someone is in relation to their stature. This is a good way of indicating whether you are at what is considered a healthy weight. Weight by itself can be misleading if someone is tall or small because a healthy tall person can weigh the same as an unhealthy smaller person.

If your BMI is between 18.5-24.9 then your weight is considered normal for your height. The World Health Organisation recommends this as a healthy weight. If your BMI is lower than 18.5 you are classed as underweight. A BMI of 25 or more classes you as you overweight and a BMI of over 30  is considered obese.

Body mass index is a commonly used figure to give an indication of the health of someone’s weight; however it is not always the best measure. There are drawbacks to the body mass index measurement, which can indicate that someone is at risk who is not. Most notable are those with a lot of muscle density throughout their body. A good example of an individual who would have a lot of muscle density would be a body builder. These individuals have an abnormal amount of weight for their height, this is achieved simply though weight training and a high protein diet.

However, having this additional weight can boost them into a high weight category on the body mass index scale. A body builder who is completely healthy or even a lot healthier than a lot of people, could be in a ‘risk category’ under the body mass index classifications.

It is for reasons like this that the body mass index scale can be misleading. A completely healthy individual can show up as at higher risk than someone who is unhealthy. Overall however it can be said that using body mass index is a fairly reliable test of weight healthiness for the overall population.

So how do you calculate your body mass index? All you need to know is your current weight and height. From these metrics you can be told instantly your current body mass index. Here is the calculation:

Metric calculation – BMI = Weight in kg / (Height (m) x Height (m))

Imperial calculation – BMI = Weight in lbs / (Height (in) x Height (in)) x 703

Or, simply use this chart to determine where you are on the Body Mass scale: