What is BMI?


BMI, or body mass index, is a measure of your body fat based on your weight and height and applies to the majority of adult men and women 20 years of age and older. While BMI does not measure your body fat directly, research has shown it is moderately correlated with more direct measures of body fat attained from skinfold thickness tests, dual energy x-ray absorptiometry (DXA), bioelectrical impedance, and other techniques. Generally speaking, obtaining BMI is an easy and inexpensive method of screening for a particular weight category (i.e. underweight, normal/healthy weight, overweight and obesity).

BMI is calculated based on the below formulas:

Formula(s) Example
Weight (lbs) / [Height (in)] x 703

Weight = 180 lbs | Height = 5’7” (67”)

Formula: [180/(67)] x 703 = 28.19

Weight (kg) / [Height (m)]

Weight = 65 kg | Height = 174 cm (1.74m)

Formula: 65/(1.74)₂ = 21.47

How do you analyze the results?

Once you’ve plugged in your weight and height into the equation(s) above and obtained your BMI, you can utilize the table below to see which category you fall into.

bmi chart

Additionally, the BMI ranges for adults and their associated weight categories are as follows:

Weight Category Body Mass Index
Underweight <18.5
Healthy 18.5 – 24.9
Overweight 25.0 – 29.9
Obese >30.0


How accurate is BMI in indicating body fat?

There is a strong correlation between BMI and body fat, however two individuals who have similar BMI’s can certainly have body fat percentages that differ from one another.

At the same BMI…

  • Women are likely to have more body fat compared to men
  • Older individuals are likely to have more body fat compared to younger individuals
  • African Americans are likely to have less body fat than Caucasians
  • Caucasians are likely to have less body fat than Asians
  • Athletes are likely to have less body fat compared to non-athletes

BMI is commonly used to assess the number of individuals who fall into a BMI range of Overweight – Obese (25.0 – 30.0+). The prevalence of obesity has continued to rise and is considered one of the world’s biggest epidemics. In the US alone, it is estimated that more than one-third of adults can be classified as obese. Obesity-related conditions can include, but are not limited to, heart disease, type 2 diabetes, and stroke, amongst many others.

Sustaining a healthy BMI can support longevity and assist in overall wellbeing. Maintaining a healthy diet, a regular fitness program and consuming adequate amounts of water are all factors recommended to support your BMI and overall health.