What is a BMI?

A BMI is a body mass index, using a BMI Calculator can give you a score that refers to a certain category seen below. It is a calculation of bodyweight and height to assess the health risk your weight carries with it. The BMI assumes that there is no one given weight that is suited for a particular height, rather, there is a range of weight for a certain height that will fit each weight category. However, BMI does not give information on body composition, instead giving the desirable weight of an average person not an elite sportsperson. Therefore, a sportsperson with 5% body fat can be classed as overweight or obese due to their increased muscle mass. See below for the ranges of BMI that are best for you.

BMI Calculator
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BMI Meaning and Charts

BMI classification refers to the health risk each category possesses. The lowest health risk sits with the ‘normal’ weight category, whilst there is an increasing health risk as you move down the categories to severely obese. However, having a score that is underweight in this table will also increase the health risk.

The score from the calculator above will sit in these categories. These can show you how close you are to hitting the next stage, set your goals in relation to this. Don’t be disheartened if you move from ideal to overweight after exercising for a period of time. This could mean that you have changed your fat into muscle. Use your eyes and see how the body has changed whether for the good or the bad.

Very Obese40+
BMI Categories
BMI ScoreClassification of BMI
20-24.9‘Normal’ Weight
30-40Moderately Obese
40+Severely Obese
BMI Classification
Healthy eating to help change the BMI.

How does a BMI calculator work out your BMI?

Your body mass index is a range of weight for every given height. This means there is no one ideal weight for any height. The value you get will outline your risk of acquiring health related conditions such as, heart disease. To find your BMI you will need to have you weight in KG and height in metres ready. Input your values into the following formula or use the calculator above.

Weight/ (Height x Height) = BMI

For example, a 60kg male standing at 1.7m will have an equation looking like this.

60 / (1.7 x 1.7) = 21

Are there limitations of a BMI?

Ultimately yes. With your BMI, the value you get from the calculator will give you your associated health risk. As it is a calculation of your height and weight, it doesn’t take into consideration your body composition. Therefore, the score you get may overestimate or underestimate your body mass index. If you are athletic or have a muscular build you can be categorised as overweight, as muscle weighs more than fat. Alternatively, if your muscle mass is low your BMI can be underestimated, this is common in the older generations.

How can I change my BMI?

As the BMI is your weight in relation to your height, it can be safe to assume that by changing your weight will change your BMI score. Lean muscle weighs more than that of fat, therefore, increasing your lean muscle mass and reducing your body fat could lead you to increase your BMI rather than decrease it. In this instance you would look to combine the BMI calculator with our other calculators to give you a better idea of the areas that can be improved for the better.

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