How Much Fluid Do You Need? Just drink eight cups of water a day and you should be fine, right? Not necessarily. The well-known recommendation is a bit outdated and doesn’t take into consideration factors that can increase fluid intake. Generally speaking, women require about 90 ounces (11 cups) per day, while men should be getting around 125 ounces (16 cups) per day. How much will depend on how much water you lose via sweat. An easy way to track this is to weigh yourself immediately before your workout and then again right afterward. For every pound of body weight lost, drink an additional 2-3 cups of water.