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BMI Calculator

Find Your BMI

Body mass index is a quick check on whether your weight is in proportion to your height. It tends to be the first figure a provider looks at in any conversation about weight, and many treatment guidelines are built around it. You can find yours below in a matter of seconds.

Keep in mind that BMI is a rough guide. It has no way of seeing muscle, bone, or where your body stores fat, so please read the notes further down before deciding what your number means. Running the body fat calculator as well will give you a fuller picture.

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Your result will show hereAdd your height and weight, then select Calculate.

How to Read Your BMI

The categories below follow the adult classification set by the World Health Organization, which the CDC also uses. They are intended for people aged 20 and older. A category points to a possible concern. It does not confirm that anything is wrong.

CategoryBMIWhat it means
UnderweightBMIBelow 18.5A low BMI is sometimes brushed aside, but it deserves attention. It may reflect a diet that is falling short, thinning bones, or a medical issue that has not yet been identified.
Healthy weightBMI18.5 – 24.9Most adults are expected to fall in this band. Even so, two people with the same BMI here can have very different blood sugar, cholesterol and fitness levels.
OverweightBMI25.0 – 29.9The likelihood of type 2 diabetes and heart disease begins to climb at this level. The concern is greater when the extra weight is carried around the abdomen.
Obesity class 1BMI30.0 – 34.9From this point, providers commonly start to discuss medical weight management, which can include GLP-1 medication alongside lifestyle changes.
Obesity class 2BMI35.0 – 39.9Health risks rise further in this band. Care plans are generally more structured, with closer follow-up from your provider.
Obesity class 3BMI40.0 and aboveAlso referred to as severe obesity. At this level the strain on the heart, joints, liver and breathing is considerably greater, and medical support is strongly advised.

Source: World Health Organization adult BMI classification, also used by the CDC. Applies to adults aged 20 and older.

How BMI Works and Where It Came From

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The calculation

BMI needs only two measurements. Using metric units, divide your weight in kilograms by the square of your height in meters. Using US units, divide your weight in pounds by the square of your height in inches, then multiply the answer by 703. Nothing else goes into the formula. Your age, your sex, your build and your fitness level play no part in it.

A short history

The idea dates back to the 1830s, when the Belgian mathematician Adolphe Quetelet was looking for a way to describe the "average" person across large groups. He was studying populations, not assessing individual patients. The name "body mass index" arrived much later, in a 1972 paper by the American researcher Ancel Keys. Medicine adopted it widely for a practical reason: all it takes is a scale and a height measurement, and anyone can work it out.

What it leaves out**

Because BMI only compares weight with height, it cannot tell what that weight is made of. A muscular athlete may land in the overweight band, while an older adult who has lost muscle may look healthy on paper despite carrying too much fat. It also says nothing about where fat is stored, and fat around the organs matters more to health than fat under the skin. Risk can begin at lower BMI values for some groups too, including many people of Asian descent, which is why a waist measurement and blood work add so much to the picture.

How BMI Affects Your Treatment Options

For all its shortcomings, BMI remains the gateway figure for most medically supervised weight loss. Prescribing guidelines for GLP-1 medications such as semaglutide and tirzepatide generally call for a BMI of at least 30. That drops to 27 for people who also have a weight-related condition, for example high blood pressure, type 2 diabetes or raised cholesterol.

Meeting that threshold opens the conversation. It does not settle it. Your provider will still go through your medical history and order lab work before deciding whether medication suits you, or whether a different approach would serve you better.

Your BMI Is Only the Starting Point

During a consultation we look at your lab results, hormone levels and health history together, so a single screening figure becomes a clear plan built around you.