Body Mass Index (BMI)

Your Body Mass Index (BMI)

The body mass index is used by some fire brigades to tell how healthy a person’s weight is, by comparing that person’s weight with their height. It is generally accepted that a person of a certain height should weigh a certain amount for their height and the BMI is used to give an indication of how under or overweight a person is.

Calculate your own BMI

  • Take your weight in kilograms (kg) and divide it by your height in metres (m).
  • Then divide the result by your height in metres (m) again.
For example:

If you weigh 80kg and your height is 1.8m, then 80 ÷ 1.8 ÷ 1.8 = 24.7. In this example, the BMI score is 24.7

Using your own BMI score, you can then compare the result to the table below, which is guidance produced by the World Health Organisation.

A score of:
  • Less than 18.4 – Underweight for your height.
  • Between 18.5 and 24.9 – Ideal weight for your height.
  • Between 25 and 29.9 – You are over the ideal weight for your height.
  • Between 30 and 39.9 – You are obese.
  • Over 40 – Severely obese.

It should be noted that this score does not account for your frame, age or any medical conditions. If you train regularly with weights and have developed muscles then your score may suggest you are overweight when in fact you are not. BMI does not relate to children or the elderly as a person’s bones in these age groups weigh less than an adult’s average. It is also not applicable to apply the BMI to women who are pregnant or people with medical conditions.

So bearing the above points in mind, if you are of average build and do not fall into any of the above exceptions, your BMI score can give an estimate of how healthy your weight is for your height.

If you scored over 25, then you are at risk from related health problems such as heart disease and high blood pressure and should consider shifting a few pounds to bring your weight down to a more healthy level. A score of over 30 will need immediate attention, as the risks from serious illness will dramatically increase, leading to possible conditions such as diabetes and other serious health problems.


If you have any concerns about your BMI, then you should consult your GP who will be able to offer help and advice.