The Ultimate Guide to the Body Mass Index (BMI) – Everything You Need to Know

The Ultimate Guide to the Body Mass Index (BMI) – Everything You Need to Know

What is Body Mass Index ?

The Body mass index is a measure of body fat based on height and weight, which is used to screen for possible weight problemsIt is commonly used to quickly classify people as underweight, overweight, or normal weight. The BMI was devised as an indicator to estimate a healthy body mass, but this has been disputed by some experts who say that it could be misleading.

Why Is The BMI Important?

The BMI is a measure that's used to assess your fitness. It doesn't take into account the muscle mass on your body, but it does take into account how much of your weight is fat as opposed to muscle. This means it can be useful for determining whether or not you're at an appropriate weight for your age and height. The BMI is also important because it can be used to assess your risk factors for certain health problems, like hypertension and type 2 diabetes.

What Factors Influence The BMI?

There are a number of factors that influence the BMI. These factors include height, weight, age and sex.


The BMI is calculated by dividing your weight (in kilograms) by the square of your height (in meters).


The BMI gives you an indication if you are underweight or overweight. You can calculate your Body Mass Index using several methods. One method is to measure in pounds and divide that figure by either 704 or 231 depending on whether the person's height is in inches or feet and inches. Another method is to measure in stones and divide that figure by 14 to get the Body Mass Index.


Younger people tend to have a higher BMI because muscle mass increases with age. As people get older, their muscle mass decreases so their BMI will decrease too. 


Women tend to have a higher BMI because they generally have more fat in their bodies than men do; but there are exceptions where women have lower BMIs than men of comparable height and weight, for example female body builders.

Healthy Weight Ranges For Men And Women

BMI is derived from a calculation of weight in kilograms divided by height in meters squared (kg/m2). A person with a BMI between 18.5 and 24.9 is considered to have a healthy weight. Below 18.5 is considered underweight and 25 or more is considered overweight.

A BMI between 25 and 29.9 is considered pre-obese, while 30 to 34.9 is considered obese. A BMI of 40 or more means that the person has morbid obesity.

How To Calculate Your BMI

To calculate your BMI, you will need to use the following equation:

BMI = Weight (kg) / Height x Height (m2)

Problems with BMI?

The BMI is a widely used measurement for health and fitness. But it does have some flaws.

1. It doesn't measure body fat percentage

The BMI is a measure of the relationship between height and weight to estimate someone's healthy weight range. It does not actually measure the percentage of body fat, but it is still widely used because it can be an effective indicator for possible weight problems.

2. BMI is set on a spectrum

The BMI ranges from underweight (less than 18.5), normal weight (18.5-24.9), overweight (25-29.9) and obese (over 30). However, the problem with this spectrum is that there are many factors that come into play that could make someone appear overweight when they may not be or vice versa, making them seem like they are in better shape than they really are, so what one person considers “normal” may not be what another considers "normal."

3. It can skew results

Another problem with the BMI is that it can lead to inaccurate results if someone who has a muscular build has a high muscle mass versus fat mass ratio or if someone who has a large frame has more bone density than others.

4. There are different measuring methods

This leads to another issue with the BMI - there are different ways to measure it, which could cause further inaccuracies in determining an individual's health risks since measurements can vary based on multiple factors such as age, gender, ethnicity.


The body mass index is an estimate of the amount of fat in your body, according to your weight and height. We hope you have found this guide to the Body Mass Index helpful. If you’re not sure whether or not you're at a healthy weight, talk to your doctor or a registered dietitian. They'll be able to help you make sure you're at a healthy weight for your height and age. 

Body Mass Index Infographics

Body Mass Index Infographics, Body Mass Index, BMI


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