How to Calculate My BMI, and What It Means

Jamie Vespa MS, RD
How to Calculate My BMI, and What It Means

According to the Centers for Disease Control and Prevention (CDC), calculating BMI (Body Mass Index) is one of the best tools for assessing overweight and obesity in the general population. The calculation only requires two metrics (height and weight), it’s inexpensive and easy to use, and it allows people to compare their weight status with that of the general population. In addition to assessing weight status, The National Heart, Lung, and Blood Institute calls BMI a useful gauge for risk of diseases that can occur with increased body fat. The institute reports that the higher a person’s BMI, the higher his or her risk of heart disease, high blood pressure, type 2 diabetes, and even certain cancers.

Limitations of the BMI

Since BMI only takes into account height and weight, it is not a useful indicator of body fat percentage or distribution of body fat. Factors such as muscle mass, bone mass, and ethnic origin can alter the relationship between BMI and amount of body fat. For example, individuals with more muscle mass who exercise often are likely to have a higher BMI than those with very little muscle mass who exercise less frequently. In this case, a higher BMI does not directly correlate to a lower standard of health.

Using only BMI, we’re also not identifying those at risk of unhealthful fat distribution, which can also make a difference in determining disease risk. Carrying excessive weight in the abdominal area, as opposed to the lower body areas like hips and thighs, puts one at greater risk for heart disease, diabetes, high blood pressure, and some cancers. For this reason, looking at both BMI and waist measurement metrics can give a more complete picture of weight status and risk of chronic disease.

How to Calculate my BMI

To calculate BMI, refer to the CDC’s Healthy Weight page, which offers a user-friendly BMI calculator.

  • If your BMI is less than 18.5, it falls within the underweight range.

  • If your BMI is 18.5 to 24.9, it falls within the normal or Healthy Weight range.

  • If your BMI is 25.0 to 29.9, it falls within the overweight range.

  • If your BMI is 30.0 or higher, it falls within the obese range.

After determining your weight status based on BMI, measure your waist circumference and compare it to the parameters below:

  • Men: waist circumference under 40 inches is within healthy range.

  • Non-pregnant woman: waist circumference under 35 inches is within healthy range.

  • Waist circumferences that are 35 inches for women and 40 inches for men indicate an increased health risk, no matter if BMI is healthy, overweight or obese.

Bottom Line

Although there are limitations, BMI can be a useful tool as a piece to the overall health picture. Some healthcare professionals find it to be most useful in identifying those in the obese category (a BMI of 30.0 or greater), which most likely have excess body fat linked to both current and future morbidity.

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