Before we begin, I want to make one thing clear, this article is written based on the assumption that your goal is a weight that is considered medically healthy. In the end no one can answer the question "how much should I weigh?" other than yourself if your goal is something outside the realm of standard health. For example if your actual question is "I'm a professional body builder, what is my perfect weight?" that answer is not something I will be able to provide.
That being said let's get down to it shall we?
The way to answer "how much should I weigh" is actually quite simple and all comes down to the math. Medical science has provided us with a height to weight ratio called our Body Mass Index (known as BMI from here on out) which, when calculated for an individual, gives them a value that falls on a scale of underweight, normal weight, overweight, and obese.
Therefore in order to find your perfect weight we must take the equation for calculating our BMI and assume a value within the healthy weight range, after that it's simply solving for the unknown (your weight) this will tell you what you need to weigh to be considered healthy.
If you go by imperial units, the way to calculate your BMI is this:
BMI = (weight in pounds * 703)/(height in inches * height in inches)
for those of you in metric lands:
BMI= weight in kilograms/(height in meters * height in meters)
The ranges for BMI fall like this:
Below 18.5 is considered underweight
Between 18.5 and 24.9 is considered normal weight
25-29.9 is considered overweight
anything above 30 is considered obese
Knowing these values and the proper equation we can now determine what your weight should be! Here is an example.
Say Suzi's height is 5 feet 4 inches and wants to know how much she should weigh, she wants to be considered a healthy weight but not by much so we'll give her a BMI of 18.7 (it's always better to have a little buffer so you don't fall into the under or overweight category too easily).
First thing we'd have to do is convert her height fully into inches, in this case 5 feet is 60 inches, plus an additional 4 makes 64 inches.
Now that we have this information we just plug that into the equation:
18.7 = (weight in pounds * 703)/(64 inches * 64 inches)
18.7 = (weight in pounds * 703)/4096
18.7*4096 = weight in pounds * 703
76595.2 = weight in pounds * 703
76595.2/703 = weight in pounds
108.95 = weight in pounds
And there you have it! If Suzi was 5 feet 4 inches tall and wanted to be next to the lowest healthy weight possible, her perfect weight would be 109 pounds, easy right?