Ideal Body Weight (IBW)


It's so inspiring to see how many people have a goal weight in mind when they embark on their journey to lose some weight! They may even aim for their ideal body weight, considering factors like their age, gender, and any health conditions they already have.


We all have different body shapes and sizes! But if you know that your actual weight is significantly higher than your ideal weight, it's important to be aware that you may be at increased risk for developing certain health conditions. These could include type 2 diabetes, high blood pressure, fatty liver disease, stroke, sleep apnea, and even some kinds of cancer.



What is Ideal Body Weight (IBW)?

At its core, ideal body weight is all about keeping you safe and healthy. It's the weight at which you're at the lowest risk of dying. Another great way to think about ideal body weight is that it's the weight at which you're getting all the nutrition you need to be as healthy as can be! 


IBW is a useful formal analysis for assessing a person's weight because it provides a quick risk assessment. However, it isn't a perfect metric. IBW doesn't account for genetics or other underlying health conditions.

We're all different, and we all have a different ideal body weight. It's not uncommon for two people of the same height to have very different ideal body weights.


Methods to Calculate Ideal Body Weight

Divine Formula

The Divine Formula is a well-known equation for estimating ideal body weight using just a height measurement. We will use inches for height in the following examples. 

  • Women: ideal body weight = 45.5 kg + 2.3 kg x (height – 60) 
  • Men: ideal body weight= 50 kg + 2.3 kg x (height – 60) 

For example, a woman who is 65 inches tall, would have an ideal body weight of 57 kg.


Similarly, a man who is 75 inches tall, would have an ideal body weight of 84.5 kg. 


Broca Formula

The Broca Index, also known as the Broca formula, was created in 1871 by the French physician, surgeon, and anthropologist Paul Broca. It's used to determine a person's normal weight. The formula is pretty straightforward. It just uses the height as its input. The only difference is for women where the ideal body weight is 10% less as shown in the examples below. 


  • Men: ideal body weight:  Height – 100 
  • Women: ideal body weight: (Height – 100) * 0.9 


For example: a man who is 175 cm tall would have an ideal body weight of 75 kg. 

Similarly, a woman who is 165 cm tall would have an ideal body weight of (165 – 100) * 0.9 = 58.5 kg. 


Lorentz Formula 

  • For men: ideal body weight: (height cm – 100) – ((height – 150)/4) 
  • For women: (height cm – 100) – ((height – 150)/2)


For example: a man who is 179 cm tall would have an ideal body weight of 72 kg.

Similarly, a woman who is 165 cm tall would have an ideal body weight of 57.5 kg. 


Miller Formula 

To get an accurate calculation, this formula requires you to measure your height in feet. 


  • For men: ideal Body Weight = 56.2 kg + 1.41 kg per inch over 5 feet.
  • For women: Ideal Body Weight = 53.1 kg + 1.36 kg per inch over 5 feet.


For example, the weight of a man who is 5 feet 2 inches tall is calculated as the following:

5 feet allows for (56.2 kg) + 2 inches allows for (2* 1.41 kg) = 2.82.  The total is 56.2+2.82 = 59 kg.


Similarly, a woman who is 5 feet 5 inches tall has an ideal body weight of:

5 feet allows for (53.1 kg) + 5 inches allows for (5*1.36 kg) = 6.8. The total is 53.1+ 6.8 = 60 kg. 



Factors That Affect Ideal Body Weight

According to the National Institute of Diabetes and Digestive and Kidney Diseases, factors that can influence your body weight include:

  • Age 
  • Genetics
  • Lifestyle
  • How many hours do you sleep
  • Medications taken
  • Any health conditions


In addition, your body fat percentage and distribution, as well as your waist circumference, can assist you in determining whether your weight is within the healthy range for your individual needs.


According to the National Institute of Diabetes and Digestive and Kidney Diseases, a waist circumference of 35 inches or greater for women indicates an elevated risk of obesity-related health complications. For men, the corresponding figure is 40 inches.


What is the ideal body weight for an individual?

In general, IBW is not a definitive factor for determining an individual's health status. BMI (body mass index) is a more precise indicator that is utilized in a medical context for the diagnosis of health-related conditions. However, some general charts provide a range of weight in relation to height for both sexes. 


For men with an average height of 160 cm, the IBW is 50.8 – 60.1 kg

For women with an average height of 160 cm, the IBW is 47.2 – 57.6 kg


Importance of Ideal Body Weight

  • Health Risk Indicator. Maintaining an optimal body weight can help reduce the risk of developing chronic diseases such as cardiovascular disease, type 2 diabetes, and certain types of cancer.


  • Weight Management Goals. The primary objectives of weight loss management are to reduce body weight, maintain it over time, and prevent further weight gain. Your IBW can serve as a valuable reference point for monitoring your weight.


  • Personalized Nutritional Planning. Knowing your ideal body weight is a crucial initial step in making informed dietary decisions. It enables you to concentrate on specific food types that support optimal body function and maintain overall health.



Limitations of Ideal Body Weight

  • Does not account for muscle mass. The IBW formulas are based on the assumption that weight increases in a linear fashion with height. However, research has demonstrated that weight is not solely dependent on height. Other factors, such as body width, trunk length, and musculature, also play a role.


  • Age and body fat distribution are not considered. According to Penn Medicine, the majority of formulas yield a single body weight, rather than a range. It is worthy to mention that most of the formulas did not address or measure body composition.



  • Age and body fat distribution. It is important to note that the concept of "ideal body weight" does not take into account a number of factors that can influence an individual's health and well-being. These factors include body diversity, age, weight suppression, psychological wellness, metabolism, and individual experience. As a result, the resulting calculation may not be optimal for the patient. 


Other Health Indicators to Consider Alongside IBW

  • Body Mass Index (BMI). The BMI is a simple medical screening tool that measures the ratio of your height to your weight to estimate the amount of body fat you have. Your healthcare provider can calculate your BMI by using your weight in kilograms (kg) divided by the square of your height in meters (m²).


  • Body Fat Percentage. Your body fat percentage is a way of measuring how much of your body is made up of fat, bone, and muscle. A healthy body fat range is 25-31% for women and 18-24% for men.


  • Waist-to-Hip Ratio (WHR). calculating your WHR is one way your doctor can determine if being overweight is putting your health at risk. It determines how much fat is stored around your waist, hips, and buttocks. The WHR measures the ratio of your waist circumference to your hip circumference


Key Takeaway 

Assessing an individual's Ideal Body Weight (IBW) can be a valuable tool for understanding their health risks. It can inform decisions about whether an individual might be at risk for weight-related health conditions due to being either overweight or underweight. However, it is important to note that IBW has several limitations that must be taken into account.