Online BMI (Body Mass Index) Calculator

Your BMI (body mass index) is the measure of your weight in relation to your height. This will give you an idea of whether you are underweight, of a normal weight or overweight.

How to use the BMI calculator

In South Africa, we use the metric system (kg and cm).

  • Enter your age (years).
  • Select your gender.
  • Enter your height in centimetres (cm). 1 metre = 100 centimetres so if you are 1.53m then you will be 153cm.
  • Enter your weight in kilograms (kg).


The ideal BMI should between 20 and 25. If you are overweight or obese then you should aim for a BMI of at least 22 to return to a safe range. Women who are pregnant should first read this article on pregnancy weight gain to get an accurate account of the healthy changes in BMI during pregnancy. It is not normal or healthy for mother and child to either not gain weight or gain too much of weight during pregnancy.

Meaning of your BMI

There is a strong correlation between your BMI and body fat. The heavier you are, the greater your BMI and usually the more your body fat. Body builders may have a high BMI although their body fat content is low. This is due to the fact that muscle is heavier than protein.

Your BMI on its own is a very important indicator of whether your weight is acceptable or not. A higher BMI indicates a greater risk of several diseases including hypertension (high blood pressure), hyperlipidaemia (high blood cholesterol and other fats), diabetes mellitus (sugar diabetes) and the risk of strokes and heart attacks.

However, other factors also need to be taken into account like the circumference of your waist and abdomen. Abdominal obesity or central obesity is the accumulation of fat around the abdomen. If you have abdominal obesity although your are within a normal BMI range, you can still be at risk of the health conditions discussed above.