BMI Calculator (Metric and Imperial)

BMI icon

Calculate your BMI (body mass index) with this calculator tool. By calculating your body mass index, you can get an indication of whether your weight may be affecting your health. A BMI chart is also available. BMI is commonly used by Doctors and health professionals worldwide and is calculated using your weight and height.


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Please note:

*The results given by this bmi calculator should be used only as a guide and should not replace medical advice. Please bear in mind that, when interpreting the results of this body mass index calculator, other factors such as muscle structure and ethnic origin should be considered. For example, a person with a lot of muscle might have a higher BMI, when their body is actually perfectly healthy, due to the fact that muscle weighs more than fat.

Always speak to a Doctor or health professional for advice and guidance before making any dramatic changes to your lifestyle.

faq icon

BMI calculator - FAQ

What Is BMI?

The body mass index measurement is the calculation of your body weight in relation to your height and is commonly used as an indicator of whether you might be in a risk category for health problems caused by your weight. Using a BMI calculator such as the one on this page, you enter your weight and height measurements. Those figures are entered into the BMI formula (more on that below) to produce your current BMI reading.

You can read more about BMI in our article, What is BMI?

The BMI classifications established by the World Health Organization (WHO) are as follows:

Body Mass Index (kg/m2) Classification
less than 18.5: underweight
18.5 - 24.9: normal weight
25 - 29.9: overweight
30 - 34.9: class I obese
35 - 39.9: class II obese
40 upwards: class III obese

BMI Shortcomings

Although BMI is commonly used as a tool to indicate whether someone is a healthy weight, it is not used to definitively diagnose obesity. Indeed, people commonly choose to take several factors into consideration for this kind of diagnosis, including age, muscle-fat ratio, waist circumference, height, sex, and bone density.

It is important to remember that BMI measurements do not make a distinction between whether you are male or female, whether you have a large or small body frame, whether you have high muscle mass and the areas in which fat is distributed around your body. So, someone who has a very muscular physique (a body builder, for example) may have a high BMI without having excess fat. For this reason, BMI is not an indicator of obesity on its own.

Some alternatives methods to BMI, including the waist-hip ratio, are discussed in our article, 5 alternatives to BMI.

BMI calculations formula

BMI Formula

The official formula for BMI was devised in the 1830s by Belgian mathematician Adolphe Quetelet.

Metric BMI Formula

BMI = weight (kg) / height2 (m2)

Imperial BMI Formula

BMI = ( weight (lb) / height2 (in2) ) x 703

Learn more about how to calculate your BMI using these formulae.

BMR calculator

As well as BMI, this website also contains a BMR calculator that allows you to calculate your basal metabolic rate (the number of calories you might burn in a day if you are inactive).

If you have any questions about this calculator then please contact me.