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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.

Learn more: read our in-depth guide BMI Chart Explained: Categories & Formula to understand the topic behind this tool.

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.

Frequently asked questions

What is a healthy BMI range?
For most adults, a BMI between 18.5 and 24.9 is considered the healthy range. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above falls in the obesity range.
How do I calculate my BMI manually?
Divide your weight in kilograms by your height in metres squared (kg/m²). In imperial units: multiply your weight in pounds by 703, then divide by your height in inches squared.
Is BMI accurate for athletes and muscular people?
Not always. BMI cannot tell muscle apart from fat, so muscular athletes can score as “overweight” while being very fit. It also doesn't suit children, pregnant women or the very elderly — treat it as a screening guide, not a diagnosis.
What is the difference between BMI and body fat percentage?
BMI estimates weight status from height and weight alone. Body fat percentage measures how much of your weight is actually fat, which needs calipers, a smart scale or a scan — BMI is the quicker rough guide.
Is the healthy BMI range the same for men and women?
Yes. The WHO adult BMI cut-offs are identical for both sexes. The same BMI doesn't mean the same body composition, but the ranges apply equally.

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