BMI Calculator

BMI (Body Mass Index)

Your Body Mass Index (BMI) is a measure indicative of a healthy weight in relation to your height. Having a good weight reduces the probability of developing health-related complications, such as diabetes, high blood pressure and strokes.

BMI is calculated the same way for everyone.

Using the metric system:

Using the Imperial system:

Generally, a healthy BMI ranges from 18.5 - 25, but precisely how healthy your BMI is depends on individual factors, such as age, ethnicity and body type.

Remember that your BMI is only an indication of a healthy weight, it is not a definitive, nor a universal marker. Always consult your physician or dietician for advice regarding your weight that is custom to your individual needs.

BMI Special Cases

Women: pregnant or breastfeeding

BMI is **not** an accurate health indicator for pregnant or breastfeeding women. Hormonal fluctuations, as well as growing a baby regularly alter body weight and structure.

Infants (< 2 years)

The body composition of infants younger than 2 years of age does not compare to that of the older population. Fat percentage is much higher and body proportions are different. Furthermore, infants, especially in the first few months, are subject to rapid changes. All this makes BMI not a suitable weight health indicator for infants.

Children and Teens (2 - 19 years)

Children and teens are subject to many bodily changes and phases of growth before reaching adulthood. This makes BMI, especially during growth spurts, not a reliable indicator of a healthy weight, as its value may change from week to week. During puberty, teens gain more muscle/fat as part of healthy development. The age of puberty onset, as well as the amount of fat or muscle that develops is different between girls and boys. That is why the healthy weight range does differentiate between the sexes in this age category.

Elderly (70+ years)

As individuals get older, it gets harder to determine whether some disease has developed because of their weight, or because of old age. This means there is less conclusive research regarding healthy weight ranges for the elderly. Some research suggests that mortality increases at values below 22.0 or above 28.0. This would mean that a BMI between 22.0 - 28.0 is generally considered a healthy weight for elderly above 70 years, although again, this is not conclusive.

Muscular individuals

Muscles are denser than fat. This means a small, but muscular individual can weigh the same amount or more than someone who is noticeably larger. Regularly training your muscles makes your body more dense which, in turn, makes BMI less indicative of a healthy weight.

Asians

Individuals of Asian descent tend to have a somewhat higher body fat percentage than average. This means that at higher BMIs the risks of developing health concerns is larger for Asians. For Asians, the cut-off value for being overweight stands at 23.0 instead of 25.0.

Abnormal body structure

If you consider yourself to have an "abnormal" body structure, then BMI might not be a valid measurement for a healthy weight. Body structure abnormalities include, but are not limited to being exceptionally tall or small, missing a body part or having an extra or disfigured body part.

History of BMI

The history of the Body Mass Index (BMI) begins in the 1830s with Adolphe Quetelet, a talented Belgian scientist who made important contributions in both mathematical and humanity fields (Faerstein & Winkelstein, 2012). He combined his interest in statistics and people and tried to describe the “average man” using statistics. He was less interested in the individual, as he believed that characteristics at the population level are more telling about the nature of a society than the characteristics of any individual is (Quetelet, 1869). He developed what was then called the Quetelet Index, a simple ratio of weight to height squared. It was meant for population-level studies, not diagnosing individuals.

Fast forward to the 1970s, when Ancel Keys, an American physiologist, popularized the term “Body Mass Index.” He showed that the Quetelet Index was a reasonably useful, and relatively simple, proxy for body fat across large groups, and the name BMI stuck. It became the standard tool to classify levels of body fat, used by influential entities such as the World Health Organization (WHO). By just knowing your height and weight, anyone could get a quick, simple and, on average, fairly accurate, estimation of their bodily health.

Today, BMI is still used as a screening tool, but many health professionals emphasize combining it with other measures, like waist circumference, body fat percentage, and metabolic health markers. As is often the case with statistics, the virtue of its success is also its kryptonite. It works well on the population level, but can fail for the individual, as the calculation can become somewhat too simple for the individual (see the "Special Cases" section on this page for examples).