SuperCalc

BMI Formula

The BMI formula is straightforward: divide your weight in kilograms by your height in meters squared (BMI = kg/m²). In imperial units: (weight in lbs / height in inches²) x 703. Devised by Belgian mathematician Adolphe Quetelet in the 1830s, BMI was never meant as an individual diagnostic — it was a population-level statistical tool. Despite its limitations, it remains the most widely used screening metric for weight-related health risk worldwide.

BMI Calculator

Enter your height and weight to calculate your Body Mass Index.

cm
kg

BMI Categories

WHO classification of Body Mass Index ranges.

CategoryBMI Range
Underweight
< 18.5
Normal
18.5 – 24.9
Overweight
25 – 29.9
Obese I
30 – 34.9
Obese II
35 – 39.9
Obese III
40+

Frequently Asked Questions

What is the BMI formula?
Metric: BMI = weight (kg) / [height (m)]^2. Imperial: BMI = [weight (lbs) / height (in)^2] x 703. Both produce the same result. Example: 75 kg at 1.80 m = 75 / 3.24 = 23.1.
Who invented BMI?
Adolphe Quetelet, a Belgian mathematician and astronomer, developed the formula in the 1830s as part of his work on 'social physics.' He was looking for a simple way to classify weight at a population level. The term 'Body Mass Index' was coined much later, by Ancel Keys in a 1972 paper.
Why does the formula use height squared?
Quetelet found that body weight scales roughly with the square of height in most adults. Some researchers argue that height cubed (or an exponent of 2.5) would be more accurate, especially for very tall or very short people. The 'new BMI' formula by Nick Trefethen uses 1.3 x weight / height^2.5 — but the classic formula remains the standard.

Medical disclaimer: BMI is a screening tool, not a medical diagnosis. It does not measure body fat directly and does not account for muscle mass, bone density, age, sex, or ethnicity. Consult a healthcare provider for personalized health advice.

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