How Accurate is BMI?

How Accurate is BMI?

How Accurate is BMI

What is BMI?

BMI stands for Body Mass Index. It is one of the most common tools used by healthcare professionals and certified physical trainers to determine whether you are too heavy in proportion to your height. The BMI calculation compares you to average weights and heights. Once a BMI calculation is made, the calculation is used to see if you fall within a “normal” range. The number is also used to determine whether you have too much fat on your body.

So, how accurate is BMI? The index can be very useful when deciding on what your ideal weight should be when you are trying to lose weight. However, as helpful as the BMI calculation is, it also has significant limitations. It is very important for you to understand these limitations, as BMI can sometimes be way off the mark.


What is the Problem With BMI’s Accuracy?

There is no one scale that can truly determine what is the right weight for every single human on the planet. This is because we are all unique. We all have different heights, weights, builds, activity levels, and so on.

When making a BMI calculation, only two things are taken into consideration. The height and weight of the person. Therefore, those who have a big build or have a large amount of muscle mass, the BMI index is very inaccurate. A person who has a larger amount of muscle mass is heavier, but this does not mean that the person has a larger amount of fat. Using BMI alone, you cannot determine if this person is actually normal or overweight.

Also, when using the index for the elderly, who have less muscle mass, the BMI scale is less dependable.

Using The BMI Index the Right Way

BMI can still be a useful tool despite its shortcomings.  Practice common sense to decide what the right weight you should be aiming for is. Do not take BMI as gospel. If you have a larger build or are more muscular than most people, add 10% to the ideal weight stated for your height (DON’T CHEAT. You know your own body). Adjusting the index can help you determine a more realistic target weight. If you are of a smaller build, I recommend subtracting 10% off the base index weight.

An alternative that is a little more accurate is to measure your body fat percentage. Body fat percentage is a clearer indication of whether you need to lose weight. Even if you have a high BMI, having a healthy body fat percentage is what is important to your health. Getting an accurate body fat percentage can be challenging as well depending on your method of measurement. The tape method can be fairly accurate, but only if you measure in the correct places. The best method is water displacement, but that test can be costly.

Besides measuring your BMI or body fat percentage, keep an eye on how you feel when you are at a certain weight. If you have reached a weight and feel sluggish, and fatigued, perhaps you need to lose a little weight. On the flip side, if you look too thin or feel weak, perhaps you have lost too much of weight and need to gain a little bit.

We are all unique. One persons overweight may be another persons ideal weight even if they are the same height. You know your own body.

Please let me know if you would like FREE COACHING to help you get on your way to a better you by sending me an email at

5 Responses to How Accurate is BMI?

  1. Darren, finally an article that is honest about BMI. A huge frame guy, this just reinforces the idea that I should never be a 185lbs! Anything under 215 and I look like I have cancer… Great article! Thanks for sharing!

    • You are a prime example of someone that BMI does not work for. As you can see from the article, you would be better off with body fat measurements or a BMI modification. Thanks for the comment.

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