BMI  Body Mass Index Calculator
(1) BMI Interpretation
The Body Mass Index is intended to be a simple measure of obesity.
According to the
Centers for Disease Control and Prevention,
If your BMI is...

You are...

Under 18.5

Underweight

Between 18.5 and 24.9

Normal

Between 25 and 29.9

Overweight

30 and Over

Obese

(2) Limitations of BMI
The Body Mass Index is defined as
BMI = weight / height^{2}
where weight is in kilograms and height is in meters.
The obvious limitation of the BMI formula is that it doesn't distinguish between fat weight and (healthier) muscle weight.
Bodybuilders and other athletes can easily have a BMI in the "obese" range and in fact be extremely lean.
(3) Finding Your Ideal Weight
You can also run the formula backwards: given your height and desired BMI (defaulted here to a midrange "normal" value of 22), you can find your ideal weight:
The same limitations still apply: the BMI formula can only give an approximate target weight for typical people.
(4) Finding Required Calories
You can get a very rough estimate of the number of calories required to maintain a desired weight by multiplying weight (in pounds) by 12:
This is a minimum calorie requirement, corresponding to a fairly sedentary lifestyle.
(In other words, this is how many calories your body burns every day, without you having to do any exercise.)
(5) Calories and Weight Loss
One pound of body fat contains 3500 calories.
That means that losing a pound of fat per week is pretty doable:
just maintain a daily calorie deficit of 500 calories
(since 500 x 7 = 3500).
By contrast, one pound of muscle contains less than half as many calories.
This explains the dirty little secret behind some fad diets: they make you lose muscle (and water) instead of fat.
(Not good: you want to lose fat, not waste away.)
So avoid the fads and burn the fat: healthy weight loss is a slow and steady process.
