How many glasses of water should I drink daily?

Many people ask how many glasses of water they should drink daily. Simple guidelines exist, but individual needs vary with body size, activity, climate and health. A common rule of thumb is about eight 8-ounce glasses (about 1.9 liters) per day. Clinical guidance from health organizations frames needs differently: the U.S. National Academies suggests roughly 125 fluid ounces (3.7 liters) of total water for men and about 91 fluid ounces (2.7 liters) for women, including water obtained from foods and beverages. These targets are general; a registered dietitian or clinician can help personalize recommendations.

Signs of adequate hydration include rarely feeling thirsty and producing pale yellow urine. Thirst, dark urine, dry mouth, dizziness or reduced urine output may indicate underhydration and warrant increased fluid intake. During exercise, hot weather, fever, vomiting, diarrhea, pregnancy or breastfeeding, people generally need more fluids.

Over-drinking also carries risks. Excessive water intake without replacing electrolytes can lead to hyponatremia, a potentially serious condition characterized by low blood sodium. Athletes exercising for long periods are advised to replace both water and electrolytes.

Practical strategies help people meet goals: carry a reusable bottle, sip consistently throughout the day, drink with meals, and include water-rich foods such as fruits and vegetables. Monitoring urine color and responding to thirst are simple, effective ways to adjust intake in real time.

For practical measurement, one cup equals 8 fluid ounces (about 237 milliliters), and many reusable bottles list fluid ounces on their labels. Tracking intake with a marked bottle or app can help people meet individualized fluid goals reliably and safely.

For anyone with heart, kidney or liver disease, or for those on medications that affect fluid balance, a healthcare professional should set individualized fluid targets. Reliable resources and clinical consultation support safe, evidence-based hydration tailored to each person’s needs.