WebMD BMI Calculator

What Is BMI?

The National Institutes of Health released its BMI standards in June 1998, in an effort to ensure that doctors, researchers, nutritionists, and government organizations were all on the same page. They took the role of the old life insurance tables as a means of determining a healthy weight.

Divide your weight in pounds by your height in inches squared, then multiply the results by a conversion factor of 703 to get your BMI. The computation for someone who is 5 feet 5 inches tall (65 inches) and weighs 150 pounds is [150 / (65)2] x 703 = 24.96. The BMI calculator from below is a simpler option.

A healthy weight is defined as a BMI of 18.5-24.9; overweight is 25-29.9; and obese is 30 or more, according to the National Institutes of Health.


BMI Catagories

BMI CategoryBMI Range
Health risk
Underweight18.4 and belowMalnutrition risk
Normal weight18.5 – 24.9Low risk
Overweight25 – 29.9Enhanced risk
Moderately obese30 – 34.9Medium risk
Severely obese35 – 39.9High risk
Very severely obese40 and aboveVery high risk

BMI Chart

Bmi for Seniors

How Accurate Is Body Mass Index, or BMI?

What’s your number — under 25 or over 35? Body mass index (BMI) is a phrase that not everyone is familiar with, but knowing what it is and what your number is is critical for your health.

BMI is a basic mathematical formula that is used to calculate fatness based on height and weight. Because of the health hazards associated with being overweight, you should be aware of your BMI (that is, having a BMI of 25 or over). Excess body weight in midlife is linked to an increased risk of death, according to a study published in the New England Journal of Medicine in August 2006.

Being excessively thin and having a BMI below the recommended range (18.5 to 24.9), on the other hand, might be dangerous to one’s health.

Many health care professionals believe that BMI is a valuable tool for determining weight and health risks, but others doubt its accuracy. Some argue that getting out the tape measure and measuring your waist circumference is a better option. Or do both strategies have a place?

Measurement of Choice

For most health practitioners, BMI is the preferred measurement.

Cathy Nonas, MS, RD, an obesity expert and representative for the American Dietetic Association, says, “I think BMI is a really good and accessible screening tool.”

However, while it is a simple and inexpensive technique of weight classification screening, it is not a diagnostic tool. To completely identify health hazards, health practitioners must conduct additional assessments. These evaluations would include body fat percentage measures, nutrition history, activity practices, and family history.

Furthermore, BMI ignores factors such as age, gender, and muscle mass. It also doesn’t distinguish between lean and fat mass. As a result, some individuals, such as strongly muscled athletes, may have a high BMI despite having a low body fat percentage. Others, such as the elderly, may have a normal BMI despite the loss of muscle that comes with age.

Take basketballer Michael Jordan, for example: “His BMI was 27-29 when he was in his peak, making him overweight, but his waist size was less than 30,” explains Michael Roizen, MD.

One reason some experts believe waist circumference is a better overall health indicator than BMI is because of this.

Another point to consider is that extra body fat has an impact on your health regardless of where it is located. Some people develop weight around their stomachs (the so-called “apple” body shape). Others are “pear-shaped,” with extra weight in the hips and buttocks. People with apple forms are more likely to suffer from health problems related to obesity.

“Fat around the waist is more biologically active and can cause more harm to your health than fat around the hips,” says one expert “Roizen, co-author of You: On a Diet, concurs. “The findings reveal that waist circumference is more reliable and closely linked to obesity-related disorders.”

When BMI is 25 to 34.9, a larger waist circumference (greater than 40 inches for males and 35 inches for women) is associated with a higher risk of type 2 diabetes, high blood pressure, abnormal cholesterol levels, and heart disease, according to the National Institutes of Health.

No math is required to precisely measure your waist. Simply measure your bare midriff at your belly button with a soft tape measure. Locate your upper hip bone and take a measurement around the abdomen above it. The tape should be snug, but not painfully so.

Because we don’t have good criteria or cut points for levels of overweight, obesity, age, or height, Nonas claims that waist circumference isn’t a better tool than BMI. She also believes that accurately measuring the waistline is more difficult than accurately measuring height and weight.

Experts believe that weight is simply one factor in our disease risk. Your proportion of body fat, waist circumference, BMI, and physical activity patterns are all significant when analyzing weight and its impact on health.

Health care providers should check BMI, waist circumference, and any other risk factors for obesity-related diseases, according to the National Heart, Lung, and Blood Institute. The best judgment is made by combining all of the data.

Drawbacks of BMI

Your BMI says nothing about your body composition, such as how much muscle you have against how much fat you have. As a result, drawing inferences solely on this figure can be deceptive, particularly when it comes to the following:

Your activity level: Even if they don’t appear out of shape, someone who is inactive may have a BMI in the normal range and a lot of body fat.

“They are usually elderly folks, those who are out of shape, or those who are unwell, and they have very low levels of muscle and bone. Even if they have a lot of body fat in contrast to their lean body mass, their BMI appears to be in the normal range “According to Kahan. “In the end, they face the same hazards as persons who are overweight and have a high BMI.”

Body type: Are you more of an apple or a pear shape? Your health is affected by where your fat is stored. In general, abdominal fat, or the “apple” shape, poses the greatest health risk. The risk of heart disease and type 2 diabetes increases when fat accumulates around the waist rather than the hips. Fat that accumulates on the hips and thighs, or the “pear” shape, is less dangerous.

Age: As you get older, your idea of an optimal BMI may change. “People who are older should certainly have a little more fat on them,” Atkinson adds, “but they shouldn’t have a BMI of 30.”

He claims that persons who are “a little bit overweight” in their later years have a higher survival probability than those who are thinner. The causes for this are unknown, however, it could be related to having reserves to draw on when combating an illness. It’s difficult to say for sure because so many factors influence your health.

Ethnicity:  BMI and health risk varied significantly between ethnic groups. Asian-Americans, for example, have lower BMIs than whites and are more likely to acquire health problems, such as diabetes. Asians have a healthy BMI range of 18.5 to 23.9, which is a whole point lower than the conventional range. A BMI of 27 or above is considered obese in Asians, although the conventional BMI obesity measure is 30 or higher.

According to Atkinson, people of Indian heritage had increased health risks with lower BMIs. “A BMI of 25 or more is the accepted definition of overweight. If you’re from India, though, a BMI of 21 or 22 increases your chance of diabetes.”

Many African-Americans, on the other hand, may have a high BMI without the health problems that come with it. African-Americans had less visceral fat (fat around their organs) and higher muscle mass than whites of the same weight and BMI, according to Atkinson. As a result, an African-American with a BMI of 28, which is considered overweight by the standard chart, may be as healthy as a white person with a BMI of 25.

Beyond BMI

So, outside BMI, what additional tools are there? You should probably take out your measuring tape.

The tape measure should run around your waist at the top of your hip bones in your lower back and around to the belly button for an accurate measurement.

Waist size:  Men should keep their waist sizes under 40 inches to avoid health concerns associated with obesity. Women should not exceed 35 inches in length. There are racial distinctions yet again. According to the Joslin Diabetes Center, Asian males should restrict their waists at no more than 35.5 inches and Asian women to no more than 31.5 inches.

Waist-to-height ratio: compares the size of your waist to your height. According to Kahan, it may be even more effective than waist circumference alone. The goal is to have a waist diameter smaller than half your height.

The waist-to-hip circumference, skinfold thickness measurement, and ultrasonography are some more approaches to quantify body fat that may be more accurate than BMI alone. Your doctor can advise you on whether or not these additional tests are required.

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