While the popular recommendation is to drink eight glasses (approximately 2 liters) of water per day, actual needs can vary based on factors like age, sex, weight, physical activity levels, and overall health. The National Academies of Sciences, Engineering, and Medicine suggests a daily water intake of about 3.7 liters (or about 13 cups) for men and 2.7 liters (or about 9 cups) for women. This includes all beverages and water-rich foods.