How to calculate your Body Mass Index (BMI)

Body Mass Index, more generally referred to as BMI, is a measurement approach that is used by medical experts such as General Practitioners, dieticians and exercise physiologists as a quick, starting point to help measure whether someone is underweight, healthy or overweight.

The reading is obtained by performing a simple calculation and  provides an objective measurement that takes into account your age as well as their height.

Most BMIs will fall in between 18 and 30, where 18 is underweight and 30 is obese.

Calculate your BMI by using the calculator below. Be sure to choose the correct unit system for your measurements.

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BMI CATEGORIES

Now you have your BMI, the next step is to understand what it actually says about your health.

Healthcare practitioners use the following guidelines to understand what the number says about your health and weight status.

BMI of less than 18.5 Underweight
BMI of 18.5 – 24.9 Healthy weight
BMI of 25 – 29.9 Overweight
BMI of 30 or more Obese




WHY IS A HEALTHY BMI IMPORTANT?

Being overweight or obese increases your risk of several health problems, including:

    • type 2 diabetes;
    • stroke;
    • coronary heart disease and heart attack;
    • high blood pressure
    • some types of cancer;
    • infertility and sexual problems; and
    • mental health problems, including depression, anxiety and psychological distress.

  • HOW IS IT CALCULATED?

    So how is a BMI calculated? First, take your weight in kilos (kg) and divide it by your height in metres. Based on your height and weight, your score will provide an estimate of whether you are underweight, healthy weight, overweight, or obese.

    In addition to getting a fast snapshot of your weight, the body mass index (BMI) is a measurement that is used by doctors, nutritionists, and other health professionals to determine the likelihood of developing a chronic disease. 

    WHAT ARE THE LIMITATIONS OF THE BODY MASS INDEX?

    The body mass index (BMI) does not take into account differences in body composition because it does not differentiate between weight attributable to muscle and weight owing to fat.

    For example, an elite athlete might have a high muscle mass and a body mass index (BMI) that is higher than 25, but they might not have excess body fat. If you are actually underweight, your physician will be able to provide you with advice.

    This is why it should be analysed carefully, and considered a starting point for discussion around healthy weight and lifestyle rather than a definitive measure of wellbeing.

    WHO SHOULD NOT RELY ON THE BODY MASS INDEX?

    Although a useful tool for many people, BMI might not be appropriate for everyone. Your cultural background and whether or not you are pregnant can have an impact on the accuracy of your BMI.

  • Here are just a few groups who should not rely on BMI readings to measure their health in relation to weight.

  •   Pregnant women. Women who are pregnant should not use it because it is intended for use by adults over the age of 18, including both men and women.

  • –  Some cultural backgrounds, including Indigenous people, Pacific Islander people and  people of Asian descent.

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