What Is Ideal Body Weight and How to Calculate It 

Ideal body weight, also called lean body weight, is a family of indexes that have been used for almost 150 years. It is used in emergency settings, and its use has been reinforced during the COVID-19 pandemic. 

Read on to learn about ideal body weight and how to calculate it swiftly and easily using the AFPA Ideal Body Weight Calculator. 


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What Is Ideal Body Weight?

The term “ideal body weight” was carried over from the original IBW formula developed by French surgeon Dr. Pierre Paul Broca in 1871. He developed it as a low-cost and indirect method of assessing body composition for soldiers in the French army. 

Since then, there have been variations and updates of formulas for ideal body weight, including those developed by Robinson, Devine, Hamwi, Miller, and Hammond. Most of these variations are referred to as lean body weight formulas or by using the name of the developer, rather than the term “ideal body weight,” which can be misleading. 

How Is Ideal Body Weight Used

Ideal body weight formulas are normally used in medical settings as a way of calculating drug dosing, renal replacement dosing, and nutrition prescriptions. During the COVID-19 pandemic, emergency care specialists reinforced the use of ideal body weight rather than actual body weight as a safer, more accurate way of calculating medication dosages. 

Some health specialists carry over the use of ideal body weight formulas into consultations as a way of providing a general weight loss or weight gain goal. 

Most health specialists for whom weight is important in their coaching or treatment processes chose to use the body mass index instead of the ideal body weight because it provides a range of weight considered normal or healthy, rather than a specific number. 

Body composition may be important to consider for health reasons; having healthy muscle mass, for example, is correlated with balance and function. Additionally, a healthy composition of fat is correlated with heart and metabolic health. 

Keep in mind that body mass index and ideal body weight are indirect methods of measuring body composition. Thus, if body composition is important, other, more exact methods can be used; these include skinfolds, bioelectrical impedance analysis, dual-energy x-ray absorptiometry (DEXA), and magnetic resonance imaging. However, for most people, these methods of measuring body composition are difficult to access or out of reach. 

Some individuals and clinicians choose to use ideal body weight calculations to help people understand how their current weight compares to linearly calculated weight based on their height and sex. 

It is important to note, however, that ideal body weight is not a measure of health. If health is a concern for an individual, then it is important that they work with their primary physician to examine lab tests and overall wellness. 

How to Calculate Ideal Body Weight

There are several equations for calculating ideal body weight. The “gold standard” for calculating ideal body weight is the one that was developed by Dr. BJ Devine in 1974. It was meant to calculate the dosage of certain medications and continues to be used for this purpose. However, the use of the “Devine formula” has extended to providing an indicator of ideal body weight based on height and sex. This formula is as follows: 

Men: Ideal Body Weight (in kilograms) = 50 + 2.3 * (height in inches over 5 ft)

Women: Ideal Body Weight (in kilograms) = 45.5 + 2.3 * (height in inches over 5 ft)

Let’s take an example of a woman who is 170 cm tall (5’7”). 

If we plug it into the formula, we get the following: 

Ideal body weight = 45.5 + (2.3 x 7) = 61.6 kg or 135.8 lbs. 

OR, Use the Easy Way

AFPA has developed a tool to help you calculate ideal body weight based on a person’s sex and height. If ideal body weight is useful for you to know, skip the calculator, save some time, and click here: https://www.afpafitness.com/tools-and-resources

Main Takeaways

Ideal body weight, or lean body weight, is used in clinical settings to calculate safe drug dosages. Some health professionals choose to use it in clinical or office settings to provide patients and clients with weight gain and weight loss goals based on their height. If you want to calculate your ideal body weight or help a client to calculate theirs, you can save the simplified ideal body weight formulas, or you can use the AFPA Ideal Body Weight Calculator. 


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  1. https://www.sciencedirect.com/science/article/abs/pii/S1525861010001489 
  2. https://wellcomecollection.org/works/ptx87ejb