How to Calculate BMI Manually

Before you calculate your BMI, it’s important to understand just what BMI is… and is not. BMI is the abbreviation of ‘body mass index’, it’s a system used to pinpoint whether an individual is a healthy weight compared to his or her height. The BMI system was invented somewhere from the years 1830-1850 by Adolphe Quetelet, who was a mathematician and scientist. Despite it being almost 200 years since Quetelet created the BMI system it is still used almost exactly as he originally created it.

While BMI isn’t the only factor in determining whether someone is a healthy weight, it is still one of the main tools used to determine whether a person is overweight. Because BMI doesn’t distinguish between weight from fat and weight from muscle it isn’t accurate for extremely muscular people like those who are very athletic. In these cases alternative methods must be utilised to determine the actual fat content of the person’s body. However, for most of us BMI is a very reliable measure of whether we’re underweight, healthy weight, overweight or obese.

BMI calculations may seem like a complicated process you have no hope of understanding. That’s not true. BMI isn’t hocus pocus or any closely guarded secret withheld by scientists and doctors. If you’ve used an online BMI calculator, then you know that you insert your height and weight, and it calculates your BMI. The website usually interprets it for you or provides a convenient chart that provides information on whether you’re underweight, normal weight, overweight or obese based on the calculated number. The website calculated it for you, but you may be curious how it arrived at that figure. BMI calculations are quite simple if you understand the basic formula used. But first, let’s examine what BMI is and what BMI calculations are used for.

BMI is the measure of overall body mass. By dividing your weight by your height (squared), the BMI calculations provide a single number. Depending where that number falls on the BMI scale, it informs you if you’re underweight, normal, overweight, or obese for your height.

Because BMI doesn’t measure body fat, however, the number is often wrong when it comes to athletes or very muscular people. Muscle is heavier than fat, so for muscular people, BMI is totally inaccurate. For the majority of people, however, it’s an excellent estimate of weight in relation to height. So how is BMI calculated?

BMI calculation might seem complicated, but really isn’t.

How to calculate BMI.

There are two ways to calculate BMI depending on whether your system of measurement is imperial (pounds and inches) or metric (kilograms and meters):

In the Imperial system of measurement the formula is weight (lb) divided by height in inches squared x 703

So if a person weighs 132lb and is 66″ tall then the maths comes out as 132 / 4356 (66×66) x 703 = BMI of 21.3

By Metric the formula is weight (kg) divided by height in centimeters squared x 10,000

So if a person weighs 60kg and is 168cm tall the maths comes out as 60kg / 28224 (168 x 168) x 10,000 = BMI of almost 21.26

When it comes to interpreting the results there are four main categories of BMI results in adults, although these can also be split into six:

1) BMI below 16 – Severely underweight
2) BMI of 16-18 – underweight
3) BMI of 18-25 – Healthy weight range
4) BMI of 25-30 – overweight
5) BMI of 30-40 – Obese
6) BMI over 40 – Morbidly Obese

Alternatively, if you want the work to be done for you, simply use the free BMI calculator below.

Be Sociable, Share!

•