BMI Calculator

What is BMI?

Body Mass Index (BMI) is a quick screening number that compares your weight to your height. The formula is simple: weight in kilograms divided by the square of your height in metres (kg / m²). Because it needs only two easy measurements, BMI is one of the most widely used ways to get a rough sense of whether someone is in a healthy weight range for their height.

This calculator does the arithmetic for you and sorts the result into a standard category. It supports both metric (kilograms and centimetres) and imperial (pounds, feet and inches) — just tap the toggle and the numbers convert automatically behind the scenes.

Understanding the categories

The World Health Organization uses these adult ranges: Underweight is a BMI below 18.5, Normal is 18.5 to 24.9, Overweight is 25 to 29.9, and Obese is 30 or above. These bands are the same whatever units you enter, since BMI itself is unit-independent once converted.

BMI is a general estimate, not medical advice. It does not distinguish muscle from fat, so very athletic people may read high, and it is not designed for children, pregnant people, or older adults. Treat it as a starting point and talk to a healthcare professional about your individual situation.

How to use it

1. Choose your unit system with the Metric or Imperial toggle.
2. Enter your height — centimetres for metric, or feet and inches for imperial.
3. Enter your weight in kilograms or pounds.
4. Read your BMI number and category, which update instantly as you type.

FAQ

Is my data private?

Yes. Every calculation runs in your browser and nothing is ever uploaded or stored.

Which units can I use?

Both. Use kilograms and centimetres, or pounds with feet and inches — the tool converts for you.

Why is my BMI "high" when I feel fit?

BMI counts total weight, so muscular builds can score above the normal range even at low body fat.

Can I use this for my child?

No. Child and teen BMI uses age-and-sex percentile charts; this tool is for adults only.