Body Mass Index Calculator and Waist Measurement

Today, 64.5% of adults in the US are considered overweight or obese. How do you know if you are among them? Two simple measures, body mass index (BMI) and waist circumference, provide useful estimates of overweight, obesity, and body fat distribution.

The form below lets you calculate your Body Mass Index to determine your weight relative to your height.

Sex:
 male female
Weight:
Height:
 
 
Body Surface Area =
m2
Lean Body Weight =
kg = lbs
Ideal Body Weight =
kg = lbs
Body Mass Index =
kg/m2 =
   

Body-Mass Index (BMI)

The body-mass index (BMI) is calculated by dividing your weight (in kg) by the square of your height (in meters). A BMI greater than 25 may indicate that you are overweight, while a BMI greater than 30 generally indicates obesity.

  • A BMI of less than 18.5 is considered underweight.

  • A BMI of 18.5 to 24.9 is considered healthy.

  • A BMI of 25 to 29.9 is considered overweight.

  • A BMI of 30 or more is considered obese.

Because BMI does not show the difference between fat and muscle, it does not always accurately predict when weight could lead to health problems. For example, someone with a lot of muscle (such as a body builder) may have a BMI in the unhealthy range, but still be healthy and have little risk of developing diabetes or having a heart attack.

BMI also may not accurately reflect body fatness in people who are very short (under 5 feet) and in older people, who tend to lose muscle mass as they age. But for most people, BMI is a reliable way to tell if your weight is putting your health at risk.

Waist Measurement Also a Key Indicator

Excess weight, as measured by BMI, is not the only risk to your health. So is the location of fat on your body. If you carry fat mainly around your waist, you are more likely to develop health problems than if you carry fat mainly in your hips and thighs. This is true even if your BMI falls within the normal range.

To measure your waist circumference, place a tape measure around your bare abdomen just above your hip bone. Be sure that the tape is snug, but does not compress your skin, and is parallel to the floor. Relax, exhale, and measure your waist.

Women with a waist measurement of more than 35 inches or men with a waist measurement of more than 40 inches may have a higher disease risk than people with smaller waist measurements because of where their fat lies.