How Much Water Should You Drink Every Day?

The National Academies of Sciences, Engineering, and Medicine set an adequate intake of about 3.7 liters (125 ounces) of total water a day for men and 2.7 liters (91 ounces) for women. "Total" means everything — beverages plus the water in food, which typically supplies about 20% of the total. Take the food share out and that's roughly 9 cups of beverages for women and 12.5 cups for men. These figures describe what adequately hydrated healthy adults typically consume, not a requirement, and the classic "eight glasses" (64 ounces) was always more of a rounded, easy-to-remember guideline than a precise target.

The honest answer is that there's no single number that's right for everyone. Body size, activity level, climate, and overall diet all shift the number meaningfully, which is why a personalized estimate tends to be more useful than a flat rule.

Some people use a rule of thumb of roughly half their body weight in ounces of water per day. It's an informal shortcut, not official guidance, but it lands in the same neighborhood as the totals above for many adults, and it scales up for larger people. Treat it as a rough starting point to adjust from, not a target to hit exactly.

The baseline above assumes a fairly average day. Several common factors push actual needs higher, sometimes by quite a lot.

Yes, mostly. Coffee and tea do have a mild diuretic effect, but modern research suggests they still contribute net positive hydration for regular drinkers, not a deficit. You don't need to "cancel out" your morning coffee with extra water.

Food also matters more than most people realize — fruits and vegetables in particular can be 85–95% water by weight. Watermelon, cucumbers, oranges, and lettuce all meaningfully contribute to daily fluid intake, which is part of why building more produce into meals supports hydration too, not just nutrition. Building more produce into your meals helps here too — see how to build a balanced plate.

Rather than tracking ounces obsessively, a few simple signals can tell you most of what you need to know day to day. If you'd like practical ways to close the gap, see easy ways to drink more water.

It's possible, though uncommon in everyday life for most people. Drinking extremely large volumes of water in a short period can dilute sodium levels in the blood, a condition called hyponatremia — this is mostly a risk in endurance sports or extreme water-drinking challenges, not from sipping water throughout a normal day.

For the vast majority of people, the more common issue by far is drinking too little, not too much. If you have a kidney condition, heart condition, or another reason to be cautious about fluid intake, it's worth checking with a healthcare provider for personalized guidance rather than relying on general estimates like this one.