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The BMI is a term that’s thrown around a lot, but what exactly is BMI? And more importantly, what can yours tell you about your health? Here’s what you need to know.

Calculate my BMI

The BMI is a term that’s thrown around a lot, but what exactly is the body mass index and more importantly, what can yours tell you about your health? Enter your weight in kg and height in cms to find out where you sit within the healthy weight range chart.

What your BMI results mean

BMI (Body Mass Index) is a standard calculation of body weight in relation to height, and is used to diagnose if someone is overweight or obese. 

What my BMI means

Under 18.5 – you are considered to be underweight.

18.5 to 24.9 – you are considered to be within a healthy weight range.

25.0 to 29.9 –  you are considered to be overweight.

Over 30 – you are considered to be obese.

What is BMI?

BMI stands for Body Mass Index, and it’s a tool that’s used to measure relative health risks associated with weight. It can also give you an indication about whether you are in a healthy weight range. You can calculate yours by dividing your weight (in kilograms) by your height (in metres squared), or enter your details in our BMI finder above.


Is BMI 100% accurate?

It’s not always accurate for everybody. It doesn’t distinguish between fat and muscle, so people who have a large muscle mass will often have a high BMI, even though their body fat is in the healthy range. Plus, a healthy BMI doesn’t always correlate with good health. In fact, research shows that one in three people who have healthy BMIs are relatively unhealthy once other test results, such as blood pressure, blood glucose and cholesterol are taken into account.

One explanation is that BMI doesn’t reflect where body fat is stored, and it’s possible to have a healthy BMI, while carrying too much fat around your waist, a location that poses more of a health risk than weight carried on your hips and thighs. A 2017 study proved that point, finding that people who carry weight around their middle but have healthy BMIs are at the highest risk of death from any cause, compared to people with higher BMIs who carry the weight elsewhere.

“If I had to choose between making sure my BMI or my waist-to-hip ratio are within the ‘normal’ range, I would go for the latter,” says the University of Sydney’s Associate Professor Emmanuel Stamatakis, who co-led the study. “A high waist-to-hip ratio most likely means high amounts of abdominal fat, and we know this comes with quite serious health risks.”


Should I bother calculating my BMI?

Yes, says Dr Michelle Celander, WW Program and Science Director. “BMI provides a snapshot of how weight affects the risk of medical problems for a population of people, so while it may not be a perfect measure of medical risk for every individual, it’s still very valuable as feedback for you.

“But, while it is a good idea to calculate and know what your BMI is, no one piece of feedback about your weight or health should be viewed in isolation, so it’s really important to consider your BMI in context of other information and measurements.”


Which other measurements matter?

There are two you should take:

A) Your waist-to-hip ratio:
Divide your waist measurement (in centimetres) by your hip measurement (in centimetres). A waist-to-hip ratio of more than 0.9 for men and 0.85 for women indicates an increased health risk.

B) Your waist-to-height ratio:
Divide your waist measurement (in centimetres) by your height (in centimetres). For good health, research shows that keeping your waist circumference to less than half your height – or a ratio no bigger than 0.5 – is wise.


What can I do to lose weight?

The WW program encourages Members to focus on realistic weight-loss goals and provides the skills and techniques to help you achieve them. A good initial goal to aim for is losing 10% per cent of your body weight. Even if that’s not enough to push you into a healthy weight range, it’s a great start when you’re overweight, with research showing it’s enough to deliver health benefits, like lowering risk factors for type 2 diabetes and heart disease.