Body mass index (BMI) is a measure of body fat based on your weight in relation to your height,
shutterstock_287376878and applies to most adult men and women aged 20 and over. For children aged 2 and over, BMI percentile is the best assessment of body fat.

What is BMI?

BMI is used as a screening tool to indicate whether a person is underweight, overweight, obese or a healthy weight for their height.

If a person’s BMI is out of the healthy BMI range, their health risks may increase significantly.

BMI values are age-independent and the same for both sexes. However, BMI may not correspond to the same degree of fatness in different populations due to different body proportions.

Benefits of maintaining a healthy weight

he benefits of maintaining a healthy weight include:

An exercise plan can help you maintain a healthy BMI.
  • Fewer joint and muscle pains
  • Increased energy and ability to join in more activities
  • Improved regulation of bodily fluids and blood pressure
  • Reduced burden on the heart and circulatory system
  • Improved sleep patterns
  • Reductions in blood triglycerides, blood glucose, and risk of developing type 2 diabetes
  • Reduced risk for heart disease and certain cancers.

Excess weight increases how hard the heart has to work, it also raises blood pressure, blood cholesterol and triglyceride levels and lowers HDL (good) cholesterol levels. Excess weight can make a person more likely to develop diabetes.

Lifestyle changes that help you maintain a 3-5% weight loss are likely to result in clinically meaningful improvements in blood glucose, triglycerides and risk of developing type 2 diabetes. Greater weight loss can also help reduce blood pressure and improve blood cholesterol.

How is BMI used?

BMI is not accurate enough to be used as a diagnostic tool. However, it is used as a screening tool to identify potential weight problems in adults.

A person may have a high BMI, yet to determine if this excess weight is a health risk, a health care provider would need to complete further assessments such as:

  • Skinfold thickness measurements
  • Evaluations of diet
  • Physical activity
  • Family history
  • Other appropriate health screenings.

How to calculate BMI for adults

Belgium Statistician Adolphe Quetelet developed the BMI formula approximately 150 years ago.

The calculation of BMI is based on the following formulas:

Metric BMI Formula

Weight (kg) / Height (m)2

With the metric system, the formula for BMI is weight in kilograms divided by height in meters squared (kg/m2). Since height is commonly measured in centimeters, divide height in centimeters by 100 to obtain height in meters.

Imperial BMI Formula

(Weight (lbs.) * 703) / Height (inches)

When using pounds and inches, the formula needs to be altered slightly. Multiply your weight in pounds by 703. Divide that by your height in inches, squared.

BMI categories

The standard weight status categories associated with BMI ranges for adults are shown in the following table:

BMI Weight status
Below 18.5 Underweight
18.5-24.9 Healthy
25.0-29.9 Overweight
30.0 and above Obese

BMI of less than 18.5A BMI of less than 18.5 indicates that you are underweight, so you may need to put on some weight. You are recommended to ask your doctor or a dietitian for advice.

BMI of 18.5-24.9A BMI of 18.5-24.9 indicates that you are at a healthy weight for your height. By maintaining a healthy weight, you lower your risk of developing serious health problems.

BMI of 25-29.9A BMI of 25-29.9 indicates that you are slightly overweight. You may be advised to lose some weight for health reasons. You are recommended to talk to your doctor or a dietitian for advice.

BMI of over 30A BMI of over 30 indicates that you are heavily overweight. Your health may be at risk if you do not lose weight. You are recommended to talk to your doctor or a dietitian for advice.


BMI (Body Mass Index) Calculator