BMI Calculator

BMI introduction

BMI is a measurement of a person’s leanness or corpulence based on their height and weight, and is intended to quantify tissue mass. It is widely used as a general indicator of whether a person has a healthy body weight for their height. Specifically, the value obtained from the calculation of BMI is used to categorize whether a person is underweight, normal weight, overweight, or obese depending on what range the value falls between. These ranges of BMI vary based on factors such as region and age, and are sometimes further divided into subcategories such as severely underweight or very severely obese. Being overweight or underweight can have significant health effects, so while BMI is an imperfect measure of healthy body weight, it is a useful indicator of whether any additional testing or action is required. Refer to the table below to see the different categories based on BMI that are used by the calculator.

BMI formula

The Body Mass Index (BMI) Calculator can be used to calculate BMI value and corresponding weight status while taking age into consideration. Use the “Metric Units” tab for the International System of Units or the “US Units” tab to convert units into either US or metric units. Note that the calculator also computes the Ponderal Index in addition to BMI, both of which are discussed below in detail.

BMI limitations

Although BMI is a widely used and useful indicator of healthy body weight, it does have its limitations. BMI is only an estimate that cannot take body composition into account. Due to a wide variety of body types as well as distribution of muscle, bone mass, and fat, BMI should be considered along with other measurements rather than being used as the sole method for determining a person’s healthy body weight.

• Athletes: Athletes, particularly those who are very muscular, may have a high BMI due to increased muscle mass rather than body fat. This does not mean they are overweight or unhealthy.
• Elderly: In the elderly, BMI may underestimate body fat because older people tend to have more body fat for the same BMI as younger adults.
• Children and adolescents: For children and adolescents, BMI is age and gender-specific and is often referred to as BMI-for-age.
• Pregnancy and lactation: During pregnancy and lactation, a woman’s body composition changes, so using BMI is not appropriate.

BMI table for adults

This is the World Health Organization’s (WHO) recommended body weight based on BMI values for adults. It is used for both men and women, age 20 or older.