How to work out your ideal body weight
by Harry • 6 minutes read
Last updated: 12 Aug, 2022
In this day and age, with dieting fads and fitness gurus everywhere you look on social media , it's next to impossible to know what's really healthy. But, whether you're looking to lose fat, gain muscle or simply maintain your current figure, knowing your ideal body weight (IBW) can help you set healthy and realistic goals.
The most important thing to note when it comes to your IBW, is that there is no universal weight that everyone should aim for. Your IBW is specific to you and depends upon many individual factors, such as genetics, age, gender, muscle mass, body fat and more.
There are various methods you can use to figure out your IBW, but you should remember that there are many other factors that decide if you are healthy, besides the number on the scale. For example: if you are at your ideal weight, but you have a very high body fat percentage, you're likely to be at greater risk of heart disease and other health problems.
An IBW calculation factors in your height and your sex. One of the most common IBW methods uses the following formulas:
For men, you begin with 106 pounds for the first 5 feet of height and add 6 additional pounds for each inch over 5 feet.
For women: start with a base 100 pounds for the first 5 feet of height and add on 5 pounds for each additional inch. If you are under 5 feet in height, simply subtract 2 pounds for each inch under.
Though this may give a rough idea of a healthy weight for an individual, there are many different variations of IBW formulas:
GJ Hamwi's formula (1964)
BJ Devine's formula (1974)
JD Robinson's formula (1983)
DR Miller's formula (1983)
Body Mass Index
Body Mass Index (BMI) is used globally, as the most popular method to determine a healthy weight range.
The rules are simple:
A BMI under 18.5 indicates that a person is underweight.
A BMI between 18.5 and 24.9 represents the ideal body weight.
A BMI between 25 and 29.9 corresponds to being overweight.
A BMI over 30 indicates obesity.
A BMI calculator will simply take into account your height and weight to produce your score. Check out this height to weight table posted by the National Institute of Health to find your BMI score.
Although there are some people that fall into the 'healthy BMI range' and are also at a healthy weight, this is not always the case. In fact, due to the minimal data included in a BMI calculation, many people at healthy weights will often be considered overweight, underweight or even obese on a BMI scale.
Problems with BMI
The BMI method may be simple and easy to use, but it comes with many flaws as a result.
Many factors that aren't included in a BMI calculation will have great effects upon someone's IBW, such as:
waist measurements and overall body frame
the percentage and distribution of body fat
lean body mass
One of the most common times that a BMI measurement fails is for high performance athletes. They tend to be very healthy, with great diets and very low body fat. They carry most of their weight in muscle mass, which weighs far more than fat, so BMI calculators tend to say they are overweight or obese and would encourage them to lose weight. This, of course, would not be a healthy option for an athlete.
Another failure of BMI is that it doesn't consider ethnicity. Studies have shown that at identical BMIs, different ethnicities may have significantly different levels of body fat, which would greatly skew how healthy individuals really are, versus their BMI.
A BMI calculation is good for showing trends in the general population and perhaps even good at measuring a roughly healthy weight range for the average person, but it is certainly not specific enough to the individual to ensure accurate results.
Fortunately for children, age is considered in their BMI calculations as they are still growing. The Center for Disease Control and Prevention (CDC) factors both age and natal sex into its BMI calculations, for children between the ages of 2 and 19 years. Though this does add an aspect of individuality, it's still far from perfect.
Luckily, there are some other methods you can use to help...
The waist-to-hip ratio (WHR) is used to compare the size of an individual's waist to the size of their hips. A high ratio tends to indicate a higher level of visceral fat - this is fat stored around the major organs in the abdominal cavity.
Why is this important?
Research indicates that those with a high WHR are more likely to develop Cardiovascular Disease and diabetes.
Therefore it is much more likely that an individual with a low WHR, is more likely to have a low body fat percentage and lead a healthy lifestyle.
A 2014 study proposed that a WHR of over 0.52 may significantly increase the risk of developing heart complications. Of course, an extremely low WHR could be equally significant, as it could be a sign of malnutrition.
How to measure your WHR
Start by relaxing your stomach to ensure accurate results. Now take a measuring tape and wrap it around your waist at the narrowest part above your belly button, then do the same at the widest part of your hips.
Divide the measurement of your waist by the measurement of your hips and you have your WHR.
Combining your WHR measurement with your IBW and BMI, factors in your body composition and should give you a much better indication of whether your BMI calculation accurately represents your ideal body weight.
Body fat percentage
An extension upon WHR that could help you figure out if your current weight is healthy or unhealthy, is measuring your body fat percentage.
Although WHR aims to give an indication of your fat levels, it only considers the distribution of visceral fat (around your stomach).
For a man: 2–24% fat is considered healthy, while over 25% is classed as obesity.
For a woman: 10–31% fat is considered healthy, while more than 32% is classified as obesity
You can easily find a machine at most gyms that will measure your body fat or simply visit your doctor for a measurement.
Combining your body fat percentage, WHR, BMI and IBW should give you a great indication of whether your body composition is healthy, and therefore help identify which direction you need to go - whether that's weight gain, fat loss or simple maintenance of your current weight.
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