how to calculate required fluid intake of a person?

There are many different methods for calculating daily fluid requirements. However, a simple equation to help adults figure their fluid needs is that for every pound of body weight, you need about half an ounce of fluid intake per day. For instance, if you weigh 140 lbs., simply multiply 140 by .5 to estimate your daily fluid needs in ounces, then divide by eight to estimate your fluid needs in cups per day, rounding up to the nearest full cup. [example: 140 x .5 = 70 ounces; 70 ounces divided by 8 = 9 cups of fluid per day]

0.5 ounces x Body Weight in Pounds = Daily Fluid Requirement in ounces