How much water should an adult drink daily?

Clear guidance helps adults determine daily water needs. Health organizations such as the National Academies of Sciences recommend that men take in about 125 fluid ounces (3.7 liters) of total water per day and women about 91 fluid ounces (2.7 liters). Total water includes plain drinking water, other beverages, and the water contained in foods. The common “eight 8-ounce glasses” rule — roughly 64 fluid ounces (1.9 liters) — can be a reasonable baseline for many people, but individual needs often exceed that amount.

Factors that increase water requirements include higher physical activity, hot or humid environments, fever or illness, pregnancy and breastfeeding, and high-protein or high-fiber diets. For pregnancy, an additional roughly 10 fluid ounces (300 milliliters) is often advised; for breastfeeding, an additional roughly 24 fluid ounces (700 milliliters) may be needed. Older adults and people taking certain medications should pay attention to thirst cues and medical advice because sensation of thirst and fluid balance can change with age and health conditions.

Signs of adequate hydration include pale-yellow urine and regular urination; concentrated dark urine, dizziness, dry mouth or reduced urine output suggest a need for more fluids. Electrolyte balance matters when replacing large losses; sports drinks or oral rehydration solutions can help after prolonged heavy sweating.

A registered dietitian or clinician can tailor recommendations to individual medical conditions, medications, and lifestyle. In general, aiming for the academy recommendations for total daily water, using thirst as a guide, and adjusting for activity and environment provides a practical, evidence-based approach to daily hydration. Caution is warranted against excessive intake without electrolyte replacement because overhydration can cause hyponatremia; patients with kidney disease or heart failure should follow individualized fluid limits set by their healthcare provider. Moderate consumption of caffeinated beverages such as coffee and tea contributes to daily fluid intake.