Question: how many liters of water does a human use in a day?
Answer: So how much fluid does the average, healthy adult living in a temperate climate need? The National Academies of Sciences, Engineering, and Medicine determined that an adequate daily fluid intake is: About 15.5 cups (3.7 liters) of fluids for men. About 11.5 cups (2.7 liters) of fluids a day for women.