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BMI Calculator

Calculate body mass index in metric or imperial units.

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Your BMI

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BMI is a population screening measure, not a diagnosis. It cannot distinguish muscle from fat, and it is read differently for children, athletes, pregnant people and some ethnic groups. Speak to a clinician before acting on it.

Quick Tool Overview

The BMI Calculator works out your body mass index from your height and weight in either metric or imperial units, shows the World Health Organization category it falls into, and gives the weight range that would put you in the healthy band at your height.

What it does
Calculates body mass index and its WHO category
You give it
Height and weight, metric or imperial
You get back
Your BMI, its category and your healthy weight range
Best for
A quick screening figure to discuss with a clinician
Calculators Free, unlimited use No sign-up Runs in your browser

About the BMI Calculator

Enter your height and weight in either metric or imperial units to get your body mass index, the World Health Organization category it falls into, and the weight range that would put you in the healthy band at your height.

BMI is weight in kilograms divided by height in metres squared. It is a population-level screening measure, not a diagnosis, and it has a well-known blind spot: it cannot tell muscle from fat, so athletes routinely read as overweight while someone sedentary with low muscle mass can read as healthy. Treat the number as one rough signal alongside waist measurement and how you actually feel, and talk to a clinician before acting on it.

Key features of the BMI Calculator

Metric and imperial

Centimetres and kilograms or feet, inches, stones and pounds — enter whichever you think in.

WHO categories

The result is placed in the standard underweight, healthy, overweight and obese bands rather than left as a bare number.

Healthy weight range for your height

The actual kilogram or pound range that would put you in the healthy band, which is more useful than the index itself.

Clear about the blind spot

BMI cannot tell muscle from fat, so athletes routinely read as overweight — the tool says so instead of implying a diagnosis.

Private by design

Your height and weight are used in the browser and never sent anywhere.

How to use the BMI Calculator

  1. 1

    Choose your units

    Switch between metric (cm and kg) and imperial (feet, inches and pounds).

  2. 2

    Enter height and weight

    Your BMI is calculated as you type.

  3. 3

    Read the category

    See which WHO band you fall into and the healthy weight range for your height.

Frequently asked questions

Under 18.5 is underweight, 18.5 to 24.9 is healthy weight, 25 to 29.9 is overweight, and 30 or above is obese, using the WHO ranges for adults.

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