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How much should I weigh?
We’re all different shapes and sizes, and that’s partly why the body mass index or BMI model was devised: to give us an idea of a ‘healthy weight range’ based on our height and age.
BMI has its limitations. There are a lot of factors that can affect our weight, and the BMI model doesn’t account for all of them. But it can give someone a good general idea of whether they’re more at risk of developing health problems because of their weight.
Measuring body fat is a more complicated (but viewed by some as more accurate) way to work out whether someone is at risk of weight-related health problems. But it doesn’t tell you what your ideal weight should be: more how much body fat you need to lose to be within the ‘healthy’ range.
So while there isn’t really such a thing as an exact, ideal weight, there are models you can use to approximately determine whether your weight could put you at risk of developing health problems.
Health problems caused by being overweight
Being overweight can have serious consequences for both your health and your quality of life. However, what many people don’t realise is that the risk of health problems can begin when you are just a few pounds overweight and can get progressively more significant the more excess weight you are carrying.
Some of the health issues that have been associated with being overweight or obese include:
Some types of cancer including breast and bowel cancer
Some eating disorders and mental health issues
Beyond the health repercussions of being overweight are social and emotional ones. People who are overweight or obese are less likely to be physically active, and people who are severely obese are also much more likely to need social care than someone who is a healthy weight.
One of the best ways of understanding if you are a healthy weight is to use a body fat percentage calculator.
What is my BMI?
BMI stands for Body Mass Index. A measurement that uses a person’s height and weight to determine their weight-related health risk. BMI is usually divided into just five different categories – typically known as:
Anyone who is above the healthy weight category is at increased risk of developing health problems, and the more overweight you are, the greater these risks become.
How to work out your BMI
There are two different calculations which can be used to determine your BMI. One uses metric units, while the other uses imperial.
Mass in kilograms (kg) ÷ height in metres squared (m²)
Mass in pounds (lbs) ÷ height in inches squared (in²) x 703
However, if you don’t want to calculate your BMI manually, there are plenty of online calculators which you can use to do it for you. Like the one we have above.
What my BMI results mean
When you calculate your BMI, you’ll end up with a number as a result. This number will fit into one of the BMI categories, which will tell you your risk of developing weight-related health problems. These are as follows:
Underweight: less than 18.5
Healthy weight: 18.5 to 24.9
Overweight: 25.0 to 29.9
Obese: 30.0 to 39.9
Extremely obese: 40.0 and above
Generally, the higher your BMI results are, the more likely you are to suffer from health problems as a result. For example, a person with a BMI of 31 is more likely to develop heart problems, have a stroke or experience osteoarthritis than someone with a BMI of 21. It’s also important to note that people who fall into the ‘underweight’ category could also be at risk of health problems.
Health professionals recommend that, where possible, people try to maintain their weight so that they fall into the ‘healthy weight’ range.
Pros and cons of using BMI
While BMI can be a very valuable tool for calculating your weight-related health risk, it isn’t perfect. The biggest advantage of BMI is that it is a general measure of obesity that will work for most people. This makes it particularly useful for health researchers who are looking at the way weight changes among different populations and over time. It can also be used to gauge your general risk of obesity-related diseases.
Unfortunately, what BMI doesn’t take into account is the type of weight that you are carrying. For example, some people who workout to build muscle have excess lean tissue but very little body fat. Nevertheless, the weight of this lean tissue can cause them to fall into the overweight category, despite there being much lower risk of health issues resulting from excess muscle or lean tissue.
Meanwhile, another person can be affected by something known as ‘normal weight obesity’, which is where they fall into the normal weight range, but still have higher levels of body fat than is recommended. This excess body fat increases their risk of obesity-related diseases.
This disparity is why many health experts recommend that patients also take body fat into account when calculating BMI.
How to calculate body fat
There are several different ways to measure your body fat. However, most experts recommend that when you are calculating body fat alongside BMI, you use your waist measurement. This is because excess fat around the abdomen is considered most dangerous when it comes to the effects that it can have on your health.
Place a measuring tape around your waist at the midpoint between the bottom of your ribs and the top of your hips. For most people, this falls just above the belly button. As a general rule, if your waist measurement is above 40 inches (35 for women) you are likely to be carrying excess fat around your abdomen, which is increasing your risk of weight-related health problems.
Some people also use callipers to measure their body fat. Callipers are a handheld tool that are used to pinch excess fat on specific areas of the body. These measurements are then converted into a body fat percentage using the instructions that come with your callipers.
What my body fat results mean
Just like with BMI, high percentages of body fat can indicate that you may have an increased risk of developing obesity-related health problems like type 2 diabetes, heart disease and stroke. It’s important to be aware however, that unlike BMI, healthy body fat percentages vary between men and women and are also based on age. This is because generally, women naturally have higher levels of body fat than men do. Body fat also usually increases with age.
Pros and cons of using a body fat calculator
Having a rough estimate of your body fat percentage can also be a valuable tool in determining your approximate risk of experiencing health problems like type 2 diabetes and heart disease.
However, like BMI is a general measurement and doesn’t take into account a person’s body composition and other individual factors. Some of the methods used to calculate body fat, such as using a tape measure or callipers, are also only approximate and are not as reliable as a complete body fat analysis which can use things like density-tracing software to determine your results.
How to lose weight
If your BMI results or body fat results indicate that you might be overweight or at increased risk of experiencing weight-related health problems, losing weight can help reduce your risk and get your health back on track.
The safest and most effective way of losing weight and sustaining a healthy weight long term is to combine a calorie-controlled diet with increased levels of physical activity. If you still have concerns and you would like to talk to someone, our experienced clinicians are ready to help. They can answer any questions that you have and help you to find the right weight loss treatment.
When we present you with stats, data, opinion or a consensus, we’ll tell you where this came from. And we’ll only present data as clinically reliable if it’s come from a reputable source, such as a state or government-funded health body, a peer-reviewed medical journal, or a recognised analytics or data body. Read more in our editorial policy.