What Is BMI? A Complete Guide to Body Mass Index
What Is Body Mass Index (BMI)?
Body Mass Index, commonly known as BMI, is a simple numerical value derived from your weight and height. It was developed by Belgian mathematician Adolphe Quetelet in the 1830s and remains one of the most widely used screening tools for categorising weight status.
How Is BMI Calculated?
The BMI formula is straightforward:
BMI = Weight (kg) ÷ Height (m)²
For example, if you weigh 70 kg and are 1.75 m tall: BMI = 70 ÷ (1.75 × 1.75) = 22.9
BMI Categories
The World Health Organisation classifies BMI into the following categories:
Limitations of BMI
While BMI is a useful screening tool, it has limitations. It doesn't distinguish between muscle mass and fat mass, meaning athletes with high muscle mass may be classified as overweight despite being very healthy.
BMI also doesn't account for fat distribution. Visceral fat (around the organs) is more dangerous than subcutaneous fat, but BMI can't differentiate between them.
When Should You Be Concerned?
A BMI outside the normal range may indicate increased health risks. Underweight individuals may face risks of malnutrition, weakened immune function, and bone loss. Overweight and obese individuals face higher risks of heart disease, type 2 diabetes, and certain cancers.
What To Do Next
Use our free BMI calculator to find your score, then consult with a healthcare professional to understand what your results mean for your individual health situation.
