Body Mass Index Calculator

The Body Mass Index (BMI) gives people a general idea of whether they are overweight, underweight or in the right weight range.

Use the body mass index calculator to calculate your body mass index (BMI).

BMI

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The BMI is calculated using height and weight, the resulting number placed into one of five categories. Individuals using BMI to assess their health and weight, should aim for a number between 18.5 and 25.

  • Underweight is less than 18.5
  • Healthy range is 18.5-25
  • Overweight is 25+
  • Obese is 30+
  • Morbidly Obese 40+

Health Risks

Some issues associated with being underweight can include the development of osteoporosis, a decrease in the effectiveness of the immune system, anaemia and in women, a decrease or loss of fertility.

Being overweight, or obese carries a huge number of health consequences. These include the increased risk of asthma, fatigue, sleep apnoea, type 2 diabetes, insulin resistance, gall bladder disease, gout, hernia and osteoarthritis to name just a few.

BMI Shortcomings

The BMI has been widely adopted as a way of checking to see whether the user is in the healthy weight range, however, the formula should be used with caution. It doesn’t take into account gender, ethnicity or age.

However, it is the BMIs inability to distinguish between lean muscle mass and body fat that limits its usefulness. A person who has a very low body fat, lifts weights and has six pack abs, may be considered overweight or obese according to the BMI.

For example, let’s have look at LeBron James, NBA player and supreme athlete. He is 6’ 8”, 250lbs and 12% body fat. If we plugged those numbers into the BMI calculator we get a BMI of 27.4. LeBron James is overweight. What complete hogwash!

Avoid the BMI If...

Children should not be assessed using the BMI. At different stages as a child grows, they should have different levels of body fat. These also differ between male and female children.

The BMI may also give inaccurate results if you are pregnant, under 4' 11" (150cm) or over 6" 3' (190cm) as it tends to underestimate short people and overestimate tall people.

The BMI shouldn’t be taken as an overall health assessment. It is a single reading that should be taken in conjunction with a check of body fat content and waist circumference as well as diet and fitness assessments. These will give you a much more accurate picture of how appropriate a person’s weight is.