Body Mass Index Calculation
The body mass index equation isn't a mysterious mixture of complicated mathematical expressions. It's really quite simple, especially if you are working with the metric system. If kilograms and metres sound like Greek to you, skip to the section on using the body mass index equation with the English (pounds and inches) system.
So how do you find body mass index?
This is the formula to use with kilograms and metres:
b=BMI
k=kilograms (weight)
m=metres (height)
b=k/(m^2)
k=b*(m^2)
m^2=k/b
For example, if you are 1.6 meteres tall (1.6 squared is 2.56)
And you weigh 56 kilograms
your BMI is almost 22
22=56/2.56
Let's say you want to be at a BMI of 23 and you are 1.75 metres tall. What would your weight be at a BMI of 23 if you are 1.75 metres tall? (note that 1.75 squared is 3.0625)
Easy. The body mass index equation is:
k=b*(m^2)
k=23*3.0625
k= ~70
You can even use a variation of the body mass index calculation to compare your BMI to somone of a different height. Let's say that there's a right smart lass on the next block who is a little bit of a thing at 1.5 metres tall. She claims to weigh 45 kilos, giving her a BMI of 20. You're 1.65 metres tall, so is 45 kilos reasonable for you? Absolutely not! It would give you a BMI of only 16.5, far below what is considered a healthy weight:
b=k/(m^2)
b=45/(1.65^2)
b= ~16.5
In order to be of a similar height weight ratio as that bonny lass, your weight should be about 54.5 kilos.
k=b*(m^2)
k=20*(1.65^2)
k= ~54.5
Now what if you're working with the English system instead? Same principle with a little adjustment for converting the figures from metric to English:
b=BMI
p=pounds (weight)
i=inches (height)
b=(705*p)/i^2
p=(b(i^2))/705
i=square root ((705*p)/b)
Using the formula this way, a person of 5'3" (63") who weighs 155 pounds has a BMI of about 27.5:
b=(705 * 155)/(63^2)
b=109275/3969
b= ~ 27.5
Of course, you can skip all the body mass index equations and just use our handy-dandy bmi index calculator.
Here are some other pages you may find interesting:
Return to the Gastric Bypass Guru from Body Mass Index Calculation
