Online BMI Calculator (for Men & Women)

Updated in May 2024

Your body mass index (BMI) can help to identify issues related to obesity or malnutrition in children, adolescents, adults and older adults. 

In addition to calculating your BMI, this calculator also reveals what weight interval is best for you live an optimal quality of life. 

Weighing within your ideal weight interval can help to prevent the development of many chronic diseases, like diabetes and hypertension. 

Enter your measurements below to determine your BMI.


What is a BMI?

A BMI is a parameter used to evaluate whether your weight is ideal for you according to your height. By using your BMI, you can determine whether you are under or overweight, and it can help to diagnose health problems like obesity or malnutrition.

A BMI can be used in children, adolescents, adults or older adults. 

How is a BMI calculated?

A BMI is alculated by dividing you weight (in kilograms) by your height (in meters) squaured. This is the formula that is used: BMI - weight / (height x height). 

BMI results are reported using units of kg/m2.

How to interpret a BMI 

After calculating your BMI, it is interpreted in the following way: 

BMI value Classification
Under 18.5 kg/m2 Underweight
18.5 a 24.9 kg/m2 Normal
25 a 29.9 kg/m2 Overweight
30 a 34.9 kg/m2 Obesity, class I
35 a 39.9 kg/m2 Obesity, class II
Over 40 kg/m2 Obesity, class III

You can determine your risk for developing a chronic disease by using your BMI result. The higher the BMI, the greater the quantity of fat accumulated in the body. Having a greater fat composition puts you at higher risk for illnesses like high blood pressure, diabetes and cardiac disease.  

Importance of BMI

Knowing your BMI is important to check wheter your weight is within the ideal range for your height. It is also important to know whether you are at risk for developing a disease. In children, a BMI can help determine whether the child is growing as expected. 

In addition, you can use your BMI to understand what your ideal weight should be and check whether you are over or under the ideal weight for your height. Check out our ideal weight calculator. 

Is BMI the best way to assess your weight? 

Although BMI is considered to be an essential tool to evaluate a patient’s nutritional status, it does not take other very important factors into consideration when looking at weight.

It is a tool that can quickly determine whether weight is appropriate or not, but it is not the best way. Ideally, you should see your doctor or a registered dieitian to additionally look at other factors, like age, physical activity level, body composition, hydration status and health history. You can also see our article about body fat percentage to learn how this measurement can impact your health.

How to improve BMI

To improve your BMI, you should first see whether you are under or over the normal range. When you BMI shows you are underweight, you should see a registered dieitian for a thorough assessment. He or she can formulate a diet plan that can prioritize weight gain in a healthy way. 

On the other hand, when a BMI is in the overweight or obesity range, the registered dieititian can recommend a diet that is lower in calories. In addition to diet, you should exercise regularly. Physical activity will help to accelerate your metabolisl and help with weight loss, which will directly impact your BMI.