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BMI Calculator

Calculate body mass index from your height and weight, and see the healthy weight range for someone of your height.

Runs entirely in your browser

Please note

BMI is a general screening measure, not a diagnosis or an assessment of your health. It cannot distinguish muscle from fat and does not apply to children, pregnancy or athletes. Speak to a qualified healthcare professional about your own situation.

How to use the BMI Calculator

  1. 1Choose metric or imperial units.
  2. 2Enter your height and weight.
  3. 3Read your BMI, the category it falls in, and the healthy weight range for your height.

How it works

BMI divides weight in kilograms by height in metres squared. Imperial figures are converted first: pounds to kilograms and feet and inches to metres, so both unit systems give exactly the same answer.

The categories shown are the World Health Organization's adult thresholds — under 18.5 underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight, 30 and above obese. The healthy weight range is the reverse calculation: the weights that put a BMI of 18.5 and 24.9 at your height.

BMI is a population-level screening measure, and it has real limits on individuals. It does not distinguish muscle from fat, so athletes often read as overweight; it does not account for body composition, fat distribution, age or ethnicity, and it is not valid for children, pregnancy, or people with a very short or very tall stature. Treat it as one rough indicator among several.

The formula

BMI = weight (kg) ÷ height (m)²
weight
body mass in kilograms
height
standing height in metres

In imperial units the equivalent is 703 × weight (lb) ÷ height (in)².

Worked example

Someone 1.75 m tall weighing 72 kg

  1. Height squared = 1.75 × 1.75 = 3.0625
  2. BMI = 72 ÷ 3.0625

Result: A BMI of 23.5, which is in the healthy range. For that height, 56.7–76.3 kg is the healthy band.

Frequently asked questions

What is a healthy BMI?
The WHO considers 18.5 to 24.9 the healthy range for adults. The calculator also shows the weight range that corresponds to it at your height.
Why does BMI say I am overweight when I am muscular?
BMI only knows your height and weight; muscle is denser than fat, so a muscular build reads high. It is a known limitation of the measure, not an error in the arithmetic.
Does BMI work for children?
No. Children are assessed against age and sex percentile charts instead, because healthy body composition changes as they grow.
Is waist measurement more useful?
For some purposes, yes — waist circumference and waist-to-height ratio say more about where fat is carried, which matters clinically. BMI remains useful as a quick population-level screen.

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