Most adults need between 2,700 and 3,700 mL of total water per day. Women should aim for about 2,700 mL (2.7 liters), while men should aim for about 3,700 mL (3.7 liters). These figures, set by the National Academies of Sciences, Engineering, and Medicine, include all water you take in: from drinks, plain water, and food.
What “Total Water” Actually Means
That 2,700 or 3,700 mL target isn’t all drinking water. Roughly 20% of your daily water intake comes from food, especially water-rich fruits and vegetables like cucumbers, lettuce, celery, bell peppers, berries, and melons. So if you’re a woman aiming for 2,700 mL total, about 540 mL is already covered by what you eat, leaving around 2,160 mL (roughly nine cups) to drink. For men, subtracting the food contribution from 3,700 mL leaves about 2,960 mL (roughly twelve and a half cups) of fluids.
Coffee, tea, juice, milk, and other beverages all count toward your fluid total. The old idea that caffeinated drinks dehydrate you has been largely debunked at moderate intake levels. Plain water is still the best default choice because it has no calories or sugar, but you don’t need to get every milliliter from a water bottle.
A Weight-Based Way to Estimate Your Needs
Because body size varies so much, a simple formula gives you a more personalized number: multiply your body weight in kilograms by 30 mL. A person weighing 70 kg (about 154 pounds) would need roughly 2,100 mL of fluid per day, while someone at 90 kg (about 198 pounds) would need around 2,700 mL. This calculation is a baseline for healthy adults at rest in a temperate climate. Heat, exercise, illness, and other factors push the number higher.
How Exercise Changes the Target
Physical activity increases water loss through sweat, sometimes dramatically. During exercise, aim to drink about 200 mL of fluid every 15 to 20 minutes. That pace keeps the stomach holding 400 to 600 mL, which is the sweet spot for your body to absorb water efficiently.
After a hard workout, you typically need to replace more fluid than you think you lost. Drinking up to 150% of your estimated fluid deficit over the next few hours after exercise is the most effective way to fully rehydrate. So if you lost about 1,000 mL (1 kg of body weight) during a run, you’d want to take in roughly 1,500 mL during recovery. Weighing yourself before and after exercise is the simplest way to estimate that loss.
Pregnancy and Breastfeeding
Pregnant individuals generally need a few hundred extra milliliters per day beyond the standard 2,700 mL recommendation. Breastfeeding requires a more significant increase. Nursing mothers need about 3,800 mL (roughly 16 cups) of total water per day to compensate for the fluid used to produce milk. That’s a full liter more than the baseline for women, and it can come from any combination of food, water, and other beverages.
Why Older Adults Need Extra Attention
The general recommendation of 2,700 to 3,700 mL stays the same for adults over 50 and beyond 70. But older adults face a unique challenge: aging blunts the sensation of thirst. Physiological changes shift the body’s electrolyte balance, and cognitive changes can further impair the ability to recognize when you need water. The result is that many older adults are chronically under-hydrated without realizing it. If you’re over 65, drinking on a schedule rather than waiting until you feel thirsty is a practical strategy.
How to Tell If You’re Drinking Enough
Rather than obsessing over exact milliliters, your urine color is the most reliable real-time indicator of hydration. Pale, nearly clear urine (straw-colored) means you’re well hydrated. A slightly darker yellow signals mild dehydration and a prompt to drink a glass or two. Medium to dark yellow urine, especially if it’s strong-smelling or you’re producing less of it than usual, points to meaningful dehydration that calls for immediate fluid intake.
Frequency matters too. Most well-hydrated adults urinate six to eight times per day. If you’re going significantly less often, or your urine is consistently deep yellow by midday, your intake likely needs to increase.
Can You Drink Too Much Water?
Yes, though it’s uncommon. Your kidneys can process roughly 800 to 1,000 mL per hour at peak capacity. Drinking far beyond that rate, especially over a short period, can dilute the sodium in your blood to dangerous levels, a condition called hyponatremia. This is most often seen in endurance athletes who drink excessively during long events or in people participating in water-drinking challenges. Over a full 24 hours, the kidneys can handle 15 to 22 liters, so the risk comes from speed, not total daily volume under normal circumstances.
For everyday life, sticking in the range of 2,700 to 3,700 mL total (including food), adjusting upward for heat and exercise, and checking your urine color will keep most people well within a safe and healthy range.