Body Mass Index Calculator (BMI)

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BMI Calculator – Body Mass Index

About this Calculator

Body mass index (BMI) is a measure of body fat based on height and weight that applies to adult men and women. It is widely used in medicine and whilst it is reasonably reflective of the average population, it is criticized as the limited data it uses is not reflective of other groups such as athletes and pregnant mothers.

An athlete using the BMI calculator would be shown as being obese, despite being obviously healthy and often lean. If you don’t fit into the general norm, consider using the other calculators listed below for a more accurate evaluation of fat content and general health.

Body Mass Index (BMI)

BMI is a useful measure of overweight and obesity. It is calculated from your height and weight. BMI is an estimate of body fat and a good gauge of your risk for diseases that can occur with more body fat. The higher your BMI, the higher your risk for certain diseases such as heart disease, high blood pressure, type 2 diabetes, gallstones, breathing problems, and certain cancers.

Although BMI can be used for most men and women, it does have some limits:

  • It may overestimate body fat in athletes and others who have a muscular build.
  • It may underestimate body fat in older persons and others who have lost muscle.

The BMI score means the following:

ClassificationBMI
UnderweightBelow 18.5
Normal18.5–24.9
Overweight25.0–29.9
Obesity30.0 and Above

Waist Circumference

Measuring waist circumference helps screen for possible health risks that come with overweight and obesity. If most of your fat is around your waist rather than at your hips, you’re at a higher risk for heart disease and type 2 diabetes. This risk goes up with a waist size that is greater than 35 inches for women or greater than 40 inches for men. To correctly measure your waist, stand and place a tape measure around your middle, just above your hipbones. Measure your waist just after you breathe out.

The waist circumference tables below provide you with an idea of whether your BMI combined with your waist circumference increases your risk for developing obesity-associated diseases or conditions.

ClassificationBMI
(kg/m2)
Obesity
Class
Men 102 cm (40 in) or less
Women 88 cm (35 in) or less
Underweight< 18.5
Normal18.5–24.9
Overweight25.0–29.9Increased
Obesity30.0–34.9IHigh
35.0–39.9IIVery High
Extreme Obesity40.0 +IIIExtremely High
Men > 102 cm (40 in)
Women > 88 cm (35 in)
Underweight< 18.5
Normal18.5–24.9
Overweight25.0–29.9High
Obesity30.0–34.9IVery High
35.0–39.9IIVery High
Extreme Obesity40.0 +IIIExtremely High

Risk Factors Associated With Obesity

Along with being overweight or obese, the following conditions will put you at greater risk for heart disease and other conditions:

Risk Factors

  • High blood pressure (hypertension)
  • High LDL cholesterol (“bad” cholesterol)
  • Low HDL cholesterol (“good” cholesterol)
  • High triglycerides
  • High blood glucose (sugar)
  • Family history of premature heart disease
  • Physical inactivity
  • Cigarette smoking

For people who are considered obese (BMI greater than or equal to 30) or those who are overweight (BMI of 25 to 29.9) and have two or more risk factors, it is recommended that you lose weight. Even a small weight loss (between 5 and 10 percent of your current weight) will help lower your risk of developing diseases associated with obesity. People who are overweight, do not have a high waist measurement, and have fewer than two risk factors may need to prevent further weight gain rather than lose weight.

Talk to your doctor to see whether you are at an increased risk and whether you should lose weight. Your doctor will evaluate your BMI, waist measurement, and other risk factors for heart disease.

The good news is even a small weight loss (between 5 and 10 percent of your current weight) will help lower your risk of developing those diseases.

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