While the “eight glasses a day” rule is a simple guideline, individual water needs vary based on factors such as activity level, climate, health conditions, and diet. The U.S. National Academies of Sciences, Engineering, and Medicine recommend about 15.5 cups (3.7 liters) of fluids per day for men and 11.5 cups (2.7 liters) for women, including fluids from both beverages and food. Most healthy adults can stay hydrated by drinking when thirsty, and water is not the only source of fluids—other drinks and high-water foods (like fruits and vegetables) also contribute. Drinking too much water, though rare, can lead to hyponatremia.
Source(s):
Mayo Clinic Staff, Water: How much should you drink every day?