How to Calculate a BMI



Finding and measuring overweight and obesity

Body mass index, BMI, is used to classify weight. It is calculated as the ratio of weight in kilograms divided by height in meters squared. That is, BMI is equal to weight in kilograms divided by height in meters squared.

How about calculating your own one?

If you're underweight, less than 18.5.

Normal weight is 18.5 to 24.99.

If you're overweight but not obese, starting to worry is just above the 25.

But when you get to 30, it is classified as class 1 obese.

And above 35, it's class 2 obese.

Class 3 is over 40.

The BMI does not necessarily reflect body fat distribution. or describe the same degree of obesity in different population groups.

These categories help identify whether an individual is underweight, has a normal weight, is overweight, or falls into different classes of obesity. It's important to note that while BMI is a useful screening tool, it does not directly measure body fat or account for its distribution. Consequently, BMI might not accurately describe the same degree of obesity across different population groups. Various factors, such as muscle mass, bone density, and ethnic differences, can influence BMI readings and their implications for health. Therefore, it's essential to consider additional assessments and individual characteristics when evaluating weight status and health risks.

CPD time1m
First Published08 June 2019
Updated08 June 2019
29 June 2025
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