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How to Calculate Your BMI and What It Means
Work out your BMI, read the categories, and know what the number can and cannot tell you
Body Mass Index, or BMI, is a quick way to estimate whether your weight is in a healthy range for your height. It is not a perfect measure, but it is a useful starting point that doctors and health services use worldwide. Here is what it means and how to read your number sensibly.
What is BMI?
BMI is your weight in kilograms divided by your height in metres squared (kg/m²). The result places you in a broad category. It is popular because it needs only two numbers you already know, and it gives a consistent way to compare across people.
How to calculate your BMI
- Open the BMI calculator.
- Enter your height and weight in your preferred units.
- Read your BMI value and the category it falls into.
The calculator runs in your browser, so the numbers you type are never uploaded.
What the categories mean
The widely used adult ranges are: below 18.5 is underweight, 18.5 to 24.9 is a healthy weight, 25 to 29.9 is overweight, and 30 or above is in the obesity range. These bands are guides, not diagnoses, and the healthy range is the same for most adults regardless of age.
The limits of BMI
BMI does not measure body fat directly or show where fat is stored. Very muscular people can score high without excess fat, and the standard categories may not fit children, athletes, pregnant women, or all ethnic groups equally. Treat your number as one signal among several, alongside waist measurement and how you feel, and discuss any concerns with a healthcare professional.
Frequently asked questions
Is the calculator free? Yes, and no account is needed.
Is my data private? Yes. The math runs in your browser and nothing is uploaded.
Is BMI accurate for everyone? No. It is a general guide and less reliable for athletes, children, and pregnancy.
What should I do with my result? Use it as a starting point and consult a professional for personal advice.
Find more on our free calculators page. This article is general information, not medical advice.
