BMI or the Body Mass Index is a method of measuring body tissue mass (muscle, fat, and bone) in adult men and women, which allows you to know if you are:

  • underweight,
  • of normal weight,
  • overweight, or
  • obese.

BMI does not directly measure body fat but it can tell you whether the person is carrying too much fat. It also helps you to determine what your ideal weight should be in relation to your height.

This method of measuring the weight of a person in relation to his height helps to determine whether a person is overweight or obese and helps to know the exposure of the person to health risks.

BMI was developed by Belgian statistician, Adolphe Quetelet, near the beginning of 19th century. It is, therefore, also referred to as or Quetelet index. As late as in the seventies, when the complications of excess body weight such as diabetes, heart disease, stroke, premature mortality became known, BMI first gained importance as a health screening method in the United States.

BMI ranges and interpretation   

BMI is a measurement, expressed as kg/m2, which compares the weight and height of a person to determine if that person is overweight or obese. Generally, accepted parameters are as follows:

  • BMI of 16 to 18.5 denotes that the person is underweight.
  • 18.5 to 25 indicate that the person is of normal weight.
  • 25 and 30 kg/m2 means that the person is pre-obese or overweight.
  • BMI more than 30 kg/m2 is considered obese.
  • More than 40 indicates morbid obesity.
  • BMI of 50 or more indicates malignant obesity or super obesity.
  • Super-super obesity stands at the end of the scale with a BMI of 60 or more.

It is important to know here that the BMI calculation does not measure body fat. It only co-relates to the amount of fat in the body. As a result, athletes who have muscle bulk may have a BMI that classifies them as overweight even though they do not have an excess of body fat.

People who are mesomorphic (people with a tendency towards musculature) have a greater BMI than people who are endomorphic (People with underdeveloped musculature, soft body, and plumpness).
A person may just be overweight – that is, his or her bodyweight may be more than normal, but that person is considered obese with health risks when the weight is much more than just being overweight.

Body Mass Index for Women and Men

Body mass index for males and females are based on the same principle calculated in the same manner. There are no different parameters of measuring BMI for women and men.

Even though a man and woman may have the same body mass index, their body composition can vary. Women have a higher body fat percentage than men, while men tend to have a higher percentage of muscle mass.

Universal BMI Formula

The formula for calculating the body mass index worldwide is universal. This simply means the formula is the same for all people, irrespective of gender, age, and ethnicity.

This test is used universally in medicine and gives you a measure of kilogram per square of the unit of height.

The British formula

You can calculate your BMI by dividing your weight (in pounds) by your height² (in inches) and then multiplying that result by the metric system conversion factor of 703:

Therefore, BMI = weight in pounds/ (height in inches)² x 703.

The metric system

BMI or Body Mass Index = Weight divided by (Height)²

Therefore, BMI =  Weight in kilograms divided by (Height in meters)²

There is a third method to calculate using both the British and metric units:

BMI = Weight in lbs x 4.88 divided by (Height in meters)2

To calculate BMI, you can also use the BMI calculator and /or the BMI chart.