What is a BMI calculator?

Well, it’s not an accountant for an airline – it’s a tool to help you work out your body mass index, which helps you judge how healthy your weight is for your height.  Once you calculate your BMI, you can use the BMI chart below to categorise yourself.  The categories range from underweight to morbidly obese and the explanation of these terms also follows.

The BMI calculator works in the same way for both adults and children to produce a standardised body mass index.  However, the table below is only for adults as a child’s BMI must be interpreted differently to take account of their age.  See our Kids section for advice on whether your child’s BMI is healthy.

The BMI calculator is useful because the majority of adults in the UK are not at a healthy weight for their frame and everywhere we turn, we are faced with the warnings regarding health implications of being overweight or obese.  However, it is also detrimental to health to be underweight and so the BMI calculator is not just for those who would like to lose weight.

BMI chart 

Categories:

Underweight 

If your BMI is less than 20, the message to you is the same as for those who are over their ideal weight.  You are in danger of compromising your health if you maintain your current BMI.

Healthy weight 

 The weight range for a BMI of 20 up to 25 is quite wide and so, even if you are unhappy with your weight, if you fall into this category, you can feel reassured that your weight is not risking your well-being.

Overweight 

From the top of the overweight category to the bottom is a difference of approximately thirty pounds which means that if you land in this range, you are never more than about two stones from a healthy weight.

Obese

Being obese has a significant impact on your health and raises the likelihood and seriousness of possible problems.  The further up the scale your BMI goes, the more daunting it may appear to deal with the problem, but the more necessary too.

Morbidly obese 

Just as the name suggests, if you are morbidly obese, you are so overweight that your life is in danger.  That may or may not be an imminent threat but it is unavoidable that aspects of your health are compromised and some people in this category find themselves disabled by their weight.

I don’t think I’m in the right category!

The calculations assume a standard amount of body fat according to weight and therefore some people have a get-out clause:

• If you are lucky enough to have an athletic build, more of your body mass will be made up of muscle, which is a heavy substance.  Therefore, you can make some allowance for that and, if you are near the edge of one category, you may really belong to the lower rating.
• However, the news is not so good for older people who have lost muscle mass with the passing years.  You probably have a higher percentage body fat than a younger person with the same height and weight.  You may have to heed advice for a higher BMI.

Pear vs. Apple

BMI is not the only way to determine health risks attributable to weight.  Your waist measurement gives a better indication of how much fat you are storing in your abdomen.  Fat stored here is more likely to be damaging your vital organs, and lead to cardiovascular problems, than that annoying but not so unhealthy fat in your bottom and legs.

Risks increase with measurements above 37 inches (94cm) for men and 32 inches (80cm) for women, and significantly increase when waists measure more than 40 inches (102cm) for men and 35 inches (88cm) for women.