noun

BMI

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BMI (noun) means a number calculated from a person's weight and height, obtained by dividing weight in kilograms by the square of height in metres. It is used to place individuals into broad weight categories and, in research, to compare groups of people. Example: “The form asked for height and weight so it could work out a BMI.”

noun

A number calculated from a person's weight and height, obtained by dividing weight in kilograms by the square of height in metres. It is used to place individuals into broad weight categories and, in research, to compare groups of people.

"The form asked for height and weight so it could work out a BMI."

"Her BMI was recorded at the start of the study."

How to Use BMI

Learner’s notes

In plain EnglishA number worked out from your height and weight.

When to use it

Written in capitals without full stops. Standard in medicine, public health and insurance forms; the expanded form body mass index is used on first mention in formal writing.

Memory tip

Do not confuse BMI with BMR, the basal metabolic rate, which is an estimate of energy used at rest and a different measure entirely.

Trace the full origin ↓

Easily confused with

body fat percentage waist-to-hip ratio BMR

Common pairings

calculate BMI BMI category high BMI BMI threshold

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Fill the Gap

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The form asked for height and weight so it could work out a _____.

Etymology

An initialism of body mass index.

Origin: English

Synonyms

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body mass index Quetelet index

Frequently Asked Questions

How is BMI calculated?

Weight in kilograms is divided by height in metres squared, so a person of 70 kg and 1.75 m has a BMI of 70 divided by 3.0625, which is about 22.9. Imperial versions of the formula apply a conversion factor to pounds and inches.

Does BMI measure body fat?

No. It uses only height and weight, so it cannot distinguish muscle from fat or say where on the body weight is carried. This is a well-known limitation, which is why other measures such as waist circumference are also recorded.

Why was BMI created?

It originated as a population-level statistic for comparing groups rather than as an assessment of any one person, and it is still most defensible in that role. Its use for individuals came later and remains contested among clinicians.