BMI Calculator
Free BMI calculator: enter your height and weight to instantly get your Body Mass Index and see if you are underweight, normal, overweight, or obese.
About this tool
Body Mass Index, or BMI, is a simple number that relates your weight to your height. Doctors and fitness experts around the world use it as a quick screening tool to see whether a person is underweight, at a healthy weight, overweight, or obese. It is not a diagnosis, but it is a useful starting point.
Our free BMI calculator does the math for you instantly. Just enter your height in centimeters and your weight in kilograms, and you will see your BMI score along with the weight category it falls into. No sign-up, no app download, and your numbers never leave your browser.
How to use
Using the calculator takes less than ten seconds. Type your height in centimeters into the first box - for example, 175. Then type your weight in kilograms into the second box - for example, 70. Press the Calculate button.
Your BMI appears immediately, together with your category and the healthy weight range for your height. You can try different weights to see what range keeps you in the Normal category, which is a handy way to set a realistic goal.
The math behind it
BMI is calculated by dividing your weight in kilograms by the square of your height in meters: BMI = kg / (m x m). For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 / (1.75 x 1.75) = 22.9.
The standard categories are: under 18.5 is Underweight, 18.5 to 24.9 is Normal, 25 to 29.9 is Overweight, and 30 or above is Obese. These cutoffs come from the World Health Organization and are used worldwide.