1. Measure your weight
The amount of water intake required depends on your overall body weight.
It only makes sense that a person weighing 80 pounds would not be expected to consume as much as a person weighing 300 pounds.

2. Divide your body weight in half
Divide your weight by half to find out how many ounces of water you should drink each day.
For example, if you weigh 150 pounds: 1/2 = 75 ounces. So for someone who weighs 150 pounds, drinking 75 ounces of water per day would be optimal.

3. Activity Levels
Do you lead a sedentary lifestyle? Sitting in front of the computer the whole 8 hour shift?
Maybe you are an athlete and you are always working out at the gym or on the tracks.
Your lifestyle will greatly affect the volume of water you would be expected to consume on a daily basis.
If you are a very active person, chances are that you tend to sweat often and a great deal at that.
It is recommended that you should add 12 ounces of water to your daily total for every 30 minutes that you work out. So if you work out for 1 hour daily, you would add 24 ounces of water to your daily intake.

Credit: dailyhealthpost.com