BMI stands for Body Mass Index and is the accepted way of measuring whether or not you are overweight, underweight or maintaining an ideal weight.

It is a far more useful method of keeping track of your weight and your weight loss goals than by simply weighing yourself on scales and trying to shed a few pounds.

What Does It Represent?

Your BMI will be a number that is calculated based on your height, weight and sex. The aim of this calculation is to take all of these important factors into account before giving you an assessment.

While BMI is one good measure of determining your ideal weight, you will have to see a professional medical adviser if you are concerned for more thorough evaluation.

The good news is that it is possible to measure your body mass index in the comfort of your home since all you need to know is your weight and height and the relevant calculation.

It does not require expensive or sophisticated equipment or a visit to a gym or clinic.

How to Calculate BMI?

To calculate your own BMI you use a different calculation depending on whether you are going to be using your height in meters or inches and your weight in pounds or kilograms.

For this example, let’s assume that your weight will be weight in kilograms divided by your height in meters squared.

So, if your weight is 65 kilos and your height 1.5 meters, then you divide your weight, 65, by 1.25 (which is 1.5 squared).

For using pounds and inches you take your weight in pounds and divide by your height squared and then multiply the answer by 703. Both of these methods of calculating BMI will give you exactly the same result.

If you are mathematically challenged as I am, there are several calculators available online that will crunch the numbers for you.

How to Interpret Your Body Mass Index Value?

Once you get the final number, you have to see where you fit in the range of values on a chart. The chart values will indicate that a certain figure is under weight, in the normal range, in the overweight range or the worst case scenario – in the obese range.

Body Mass Index is commonly used as an indicator of obesity. However, it is far from perfect and there are important factors that should also be taken into account. These factors are sex, race, age and body type.

Different BMI values are healthy depending on your age, race, sex and body type. Therefore, you should take these into account also. If you are looking for one quick measure (besides your weight), then the BMI index will give you just that.

Get It Right

Some experts use a number called the BMI to determine whether a person is at a healthy weight to prevent excess fat and reduce the risk of disease.

The question is, should you be more concerned with BMI or with your body fat percentage if you are looking for the best health? By looking at how these two numbers are determined, we can figure out which one you should be most concerned with.

BMI is a relationship between your height and weight. To calculate it, you need to know your weight in kilograms and your height in meters. Once you know those two things, you divide your weight by the square of your height. The result is a single number known as your BMI.

Increased Risk of Diseases

Research has shown that a BMI of greater than 25 tends to be associated with excess body fat and an increased risk of disease. It is easy to find your height and weight, and from that calculate your Body Mass Index.

Concentrating on getting this number under 25 seems to be a good way to get fit. But there’s a problem.

BMI only takes into account your height and weight. It says nothing about your body composition. It knows nothing about how muscular you are or the size of your frame.

If you are an average person with an average build, BMI is a pretty useful number. If you aren’t average, it is misleading.

There Are Exceptions

Many top athletes have large frames and are heavily muscled, with little body fat. Thanks to the weight of all their muscle, they often have a Body Mass Index of over 25.

This number indicates that they are likely fat and at increased risk of disease, even though they are actually some of the fittest and healthiest people on the face of the Earth.

Clearly, there are some problems with blindly relying on Body Mass Index.

Body fat percentage is harder to determine than BMI. The index just requires you to plug height and weight into an equation, while there is no 100% accurate way to measure body fat.

Still, any of the techniques for measuring the Body Fat Percentage are attempts to directly measure the thing we’re most concerned about.

Remember the top athletes we talked about earlier? They might have a BMI that says they are overweight, but any decent measurement of their percentage of body fat will correctly show them to have very low body fat and be very fit.

Clearly, body fat percentage, while harder to measure exactly, is the more important of the two numbers for maintaining a lean body and minimizing your risk of disease.

What’s Your Healthy Weight?

Body Mass Index is a good way for individuals to assess their overall body picture, as it provides a reasonably sound measure of a healthy weight range.

Body Mass Index is the ratio of body weight (in kilograms) to height (in meters) squared (i.e. BMI = wt [kg] ÷ ht [m)2.

Body composition can be best assessed by what you know about yourself- i.e. what you see in the mirror and then finding out your Body Mass Index.

BMI adopted standards

The current Body Mass Index standards that have been adopted worldwide include:

  • Underweight <18.5
  • Normal, health 18.5-24.9
  • Overweight 25.0-29.9
  • Obese >30.0 (with different classes above 30.0)

This Body Mass Index can give you a quick snapshot of your body’s condition. If you are carrying a lot of fat, your BMI will be in the overweight or obese range.

Being in this range will increase the likelihood of becoming ill with things like heart disease or diabetes.

Several studies have shown that people who live the longest have a BMI of 22.5 to 23.5, although obviously other factors such as smoking and other lifestyle factors affect this.

Some allowances to BMI might be made for age (higher values) in special cases, but the above values are suitable for the vast majority of adults. The difficulty with assessing BMI as an indicator of body fat is that heavily muscled people (such as body builders) might have an artificially high BMI. Nevertheless, it is worthwhile keeping your Body Mass Index in the healthy weight range.

Most Commonly Asked Questions About BMI

The BMI is the most commonly used measure for healthy weight for height. It certainly gives a quick ball park figure of if your weight is in a healthy range. Here are answers to some of the common questions on BMI.

How do I calculate my BMI?

BMI = weight (kg) / height (m)2

What is an example of calculating BMI?

Jenny is 165cm tall and weighs 65. Her BMI is: BMI = 65/(1.65×1.65) = 23.9

What should my BMI be?

Your BMI should fall into the range of 18.5 to 25. Above 25 is considered overweight and above 30 is considered obese.

What does it mean if my BMI is above 25?

There is no need to panic if your BMI is above 25, it just means you are strongly encouraged to lose weight. For BMI’s above 25 health issues such as heart disease, stroke, diabetes and cancers start to become more apparent.

I have a thick frame, will this affect my BMI?

It certainly will. You need to take your BMI measurement with a grain of salt as well. Many athletes with a high level of muscle will find they have a high BMI. A better measure is to have your body fat % measured, which can be done at most gyms. So some people will naturally have a higher BMI as they have a heavier frame.

If BMI is not always accurate why do so many people use it?

BMI is the quickest method we have to make broad assessments on people’s weight. Over a large cross section of people BMI readings are a very good indication, however on an individual level BMI can vary depending on frame size.