Most adults need between 72 and 104 ounces of total daily water, depending on sex. The National Academy of Medicine recommends about 104 ounces (13 cups) for men and 72 ounces (9 cups) for women aged 19 and older. Those numbers include water from all sources: beverages, coffee, tea, and food.
The General Guidelines
The 104-ounce and 72-ounce targets represent total water intake, not just glasses of plain water. About 20% of your daily water comes from food, especially fruits, vegetables, soups, and yogurt. That means the amount you actually need to drink is closer to 83 ounces for men and 58 ounces for women. The old “eight glasses a day” rule (64 ounces) lands in roughly the right range for women but undershoots what most men need.
A More Personalized Formula
If you want a number tailored to your body, multiply your weight in pounds by 0.67. A 150-pound person would need about 100 ounces. A 200-pound person would need around 134 ounces. This formula gives you a baseline that accounts for the fact that larger bodies require more water to maintain normal cell function, regulate temperature, and support circulation.
Keep in mind that this is a starting point. Your actual needs shift based on how active you are, where you live, and your overall health.
Adjustments for Exercise
Physical activity increases your water needs, but the right approach is simpler than you might expect: drink when you’re thirsty during exercise, not on a rigid schedule. After your workout, weigh yourself. For every pound you’ve lost, drink 16 to 24 ounces of fluid to replenish what you sweated out.
One important ceiling to know: drinking more than about 27 ounces (800 mL) per hour during exercise is not recommended. Going beyond that rate can actually dilute the sodium in your blood, a condition that causes nausea, confusion, and in rare cases, serious complications.
Pregnancy and Breastfeeding
Pregnant women generally need a few extra cups per day beyond the standard 72-ounce recommendation. Breastfeeding increases the requirement further because milk production draws directly from your body’s water supply. Nursing mothers produce roughly 24 ounces of milk per day on average, and expert guidelines recommend adding about that same volume in extra water, bringing the daily total to around 96 ounces or more.
Why Older Adults Need Extra Attention
Adults over 65 face a specific challenge: the thirst signal weakens with age. In one study, healthy older men who were deprived of water for 24 hours reported no meaningful increase in thirst or mouth dryness compared to younger participants. That blunted thirst response, combined with reduced kidney efficiency, makes older adults significantly more prone to dehydration even when water is readily available.
The fluid targets for older adults are similar to those for younger adults, roughly 54 to 68 ounces of beverages per day depending on sex. But because thirst is unreliable, drinking on a schedule or keeping a water bottle visible throughout the day becomes more important than it is for younger people.
How to Tell If You’re Drinking Enough
Urine color is the simplest real-time indicator of hydration. Pale yellow means you’re well hydrated. As your body becomes more dehydrated, urine darkens progressively, shifting from light straw to deep amber. The color change tracks closely with how concentrated your urine is: after drinking water, concentration drops to low levels and urine runs nearly clear, while overnight water deprivation can push it to five times that concentration, producing dark yellow or brownish urine.
If your urine is consistently pale to light yellow throughout the day, you’re almost certainly hitting your target regardless of how many ounces you’re counting. Dark urine first thing in the morning is normal after hours without drinking, but if it stays dark into the afternoon, you’re behind.
Can You Drink Too Much?
Yes. Your kidneys can process roughly 27 to 33 ounces of water per hour. Drinking significantly beyond that rate, especially over a short period, can overwhelm your kidneys and dilute blood sodium levels. This condition, called hyponatremia, causes symptoms ranging from headache and nausea to seizures in extreme cases. It’s rare in everyday life but does occur in endurance athletes and people who force large volumes of water in a short window.
For most people, the practical takeaway is straightforward: spread your intake across the day rather than chugging large amounts at once. Sipping consistently is both safer and more effective at maintaining hydration than playing catch-up.
Putting It Together
Start with the baseline: 104 ounces for men, 72 ounces for women, from all sources including food. If you want a weight-based number, multiply your pounds by 0.67. Add 16 to 24 ounces for every pound lost during exercise. And rather than obsessing over exact counts, let your urine color serve as a running check. Pale yellow means you’re on track.