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- Which parameters are required to calculate your BMI?
- Discover the formula for calculating your BMI
- What does the BMI indicator tell us?
- The BMI: A formula endorsed by the WHO yet still a subject of controversy
- The history and objective of the Body Mass Index (BMI)
- Adolphe Quetelet’s multiple talents
- All the formulas for calculating your ideal weight
The BMI (Body Mass Index) is a simple mathematical formula validated by the WHO (World Health Organization) and which indicates an individual’s body weight relative to their height. The BMI ranges from thinness to obesity. However, this very simple formula, “BMI = Weight / Height²”, does not differentiate between men, women and different types of morphology (bone structure), and is therefore much less reliable than the ideal weight calculator (Lorentz formula). The tool below will allow you to calculate your BMI.
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Which parameters are required to calculate your BMI?
- Body weight
- Height
Discover the formula for calculating your BMI
BMI = Weight / Height²
What does the BMI indicator tell us?
This index has enabled the WTO to establish a reference classification in terms of overweight. The aim of this international classification is to measure the risks associated with overweight and obesity. By regularly calculating your BMI, you can monitor your own weight trends. Please note that this BMI formula is only for adults aged between 18 and 65 (except pregnant women and top-level sportspeople).
A “Normal” BMI is therefore between 18.5 and 24.9. If your result is below 18.5, you are considered to be thin. Above 25, you are either overweight (between 25 and 30) or obese (>30). The table below gives you the precise interpretation depending on your result.
BMI is just an index, but it should alert you if it is high. A high BMI increases the risk of developing certain illnesses such as high blood pressure, cardiovascular disease, type 2 diabetes, etc. To reduce your BMI, you are advised to rebalance your diet and take up physical activity.
Let’s take an example:
For example, if you are 1.80 m tall and weigh 80 kg: BMI = 80 / (1.8*1.8) = 24.7 In this case, with our BMI example of 24.7, we are in the “Normal” category.
Understanding the Body Mass Index (BMI) chart
| BMI result | BMI interpretation |
|---|---|
| BMI<16.5 | Undernutrition |
| 16.5<BMI<18.5 | Leanness |
| 18.5<BMI<25 | Normal build |
| 25<BMI<30 | Overweight |
| 30<BMI<35 | Moderate obesity |
| 35<BMI<40 | Severe obesity |
| 40<BMI | Morbid obesity |
The BMI: A formula endorsed by the WHO yet still a subject of controversy
The BMI is officially recognised as a statistical tool by the World Health Organisation , but is still widely disputed by health professionals. The Body Mass Index is calculated simply on the basis of weight and height, without taking into account the person’s sex, morphology or age.
If we take the example given above of a man measuring 1.80 m and weighing 80 kg, we can see that this person is borderline overweight. If this person weighs 81kg for 1.80, their status changes to “overweight”.
Needless to say, you’ll have no trouble finding athletic men around you with this weight/height ratio who are neither overweight nor have excess body fat.
This is a perfect example of the limitations of the BMI, which puts men and women on an equal foot ing without taking into account the morphology of the person being analysed.
The history and objective of the Body Mass Index (BMI)
The Body Mass Index (BMI) was introduced in the mid-19th century by the Belgian mathematician Adolphe Quetelet. It was initially designed to assess malnutrition and infant mortality in populations, rather than to assess individual health and ideal body weight. Over the years, however, it has become commonly used to assess obesity and a person’s physical condition, although this was not its original purpose.
Adolphe Quetelet’s multiple talents
Adolphe Quetelet was a Belgian mathematician, statistician and philosopher. He is regarded as one of the founders of modern statistics and devoted much of his career to the study of health and nutrition in populations. He also worked on other subjects such as meteorology, demography and criminology.
All the formulas for calculating your ideal weight
The Lorentz formula, created by Dr Friedrich Lorentz (a member of the Department of Sports Hygiene at the Hamburg Institute) in 1929, is based on the Broca Index and it contains additional parameters, such as the person’s height and sex.
Advantage: It is the most common formula used these days to estimate your ideal weight.
Disadvantage: It’s an approximate formula as it does not take into account age or morphology.
Ideal weight for men(in kg) = Height (in cm) – 100 – ((height in cm – 150) /4))
Ideal weight for women(in kg) = Height (in cm) – 100 – ((height in cm – 150) /2.5))
The Body Mass Index (BMI) is based on a weight-to-height ratio and it is used to determine and assess the risks associated with being underweight or obese.
In order to provide an even more accurate estimate of your ideal weight, this formula takes into account another parameter in addition to your height: your bone structure.
Advantage: It includes bone structure its calculation, and muscle mass to a certain extent.
Disadvantage: The calculation formula is approximate.
Ideal weight (in kg) = (Height in cm – 100 4 x Wrist circumference in cm) / 2
This is the oldest formula to calculate your ideal body weight: It was invented by Dr Paul Broca, a French surgeon, in 1871.
Advantage: It’s a simple formula that is easy to calculate.
Disadvantage: It’s an approximate calculation: It overestimates weight, not only for women, but also for anyone who is taller than 1.65 m.
Ideal weight (in kg) = Height (in cm) – 100
Dating back to 1891, Bornhardt’s formula was originally devised to determine the build of people enrolled in the army and thus determine their physical aptitude for military service. Although less popular than Broca’s Index, it is nonetheless more reliable and accurate, since it takes into account the individual’s specific build.
Advantage: It includes the chest circumference and, to a certain extent, muscle mass.
Disadvantage : It’s an approximate calculation.
Ideal weight (in kg) = ((Height (in cm) x Chest circumference (in cm)) / 240
The formula was created by Professor AF Creff in the 1970s, and it offers a precise calculation of your ideal weight, provided that you have an accurate estimate of your body shape and type.
Advantage: It incorporates body morphology into its calculation, in addition to height and age.
Disadvantage: This formula is based on the distinction between “normal”, “broad” and “slender” people. These notions are relatively vague and subjective and thus the calculation remains fairly approximate.
For an individual with a “normal” build:
Ideal weight (in kg) = Height (in cm) – 100 (Age (in years) /10) x 0.9
For an individual with a “large” build:
Ideal weight (in kg) = Height (in cm) – 100 (Age (in years) /10) x 0.9 x 1.1
For an individual with a “slender” build:
Ideal weight (in kg) = Height (in cm) – 100 (Age (in years) /10) x 0.9 x 0.9
This formula was devised by Dr B.J. Devine in 1974. It was originally designed for medicinal dosage purposes. Widely used in English-speaking countries, this formula was employed by major medical and pharmaceutical houses between 1974 and 2000.
Advantage: It allows a given height, measured in inches, to be converted into an ideal weight, in kilograms.
Disadvantage: The formula does not take age into account, thus it remains approximate.
Ideal weight for men (in kg) = 50 (kg) 2.3 x [Height (in inches) – 60]
Ideal female weight (in kg) = 45.5 (kg) 2.3 x [Height (in inches) – 60]
* one inch represents 25 centimetres
The Perrault Formula is also a variation of Broca’s formula.
Advantage: This formula uses age in its calculation.
Disadvantage: It does not take sex into account. Approximate calculation formula.
Ideal weight (in kg) = Height (in cm) – 100 + (age (in years)/10) x 0.9
