Updated November 2026
Quick answer: the U.S. National Academies suggest a total daily water intake of about 3.7 liters (125 oz) for men and 2.7 liters (91 oz) for women, counting water from all drinks and food. Since food supplies about 20%, that works out to roughly 13 cups of fluids a day for men and 9 cups for women.
General information, not medical advice. If you have heart, kidney or liver problems, follow your doctor's advice on fluids.
Daily water needs at a glance
| Group | Total water a day | From drinks (about 80%) |
|---|---|---|
| Men | 3.7 L (125 oz) | About 3 L (13 cups) |
| Women | 2.7 L (91 oz) | About 2.2 L (9 cups) |
| Pregnant | 3.0 L (101 oz) | About 2.4 L (10 cups) |
| Breastfeeding | 3.8 L (128 oz) | About 3 L (13 cups) |
One cup is 8 fl oz (about 240 ml). These are averages for healthy adults in a mild climate, not strict targets. Your needs go up in hot weather, at high altitude, when you exercise and when you're ill with fever, vomiting or diarrhea.
Water needs by body weight
A popular rule of thumb is to drink about half an ounce of water per pound of body weight (about 30 to 35 ml per kg). It's a rough guide, not an official recommendation:
| Body weight | About 0.5 oz per lb | In liters |
|---|---|---|
| 120 lb | 60 oz | 1.8 L |
| 140 lb | 70 oz | 2.1 L |
| 160 lb | 80 oz | 2.4 L |
| 180 lb | 90 oz | 2.7 L |
| 200 lb | 100 oz | 3.0 L |
| 220 lb | 110 oz | 3.3 L |
Calculate your daily water intake →
Drinking more when you exercise
- Before: drink about 16 to 20 oz (0.5 to 0.6 L) a couple of hours before a hard workout.
- During: sip regularly. Many people need about 0.4 to 0.8 L an hour, more in the heat.
- After: weighing yourself before and after a long session shows how much you lost. Drink about 1.5 times the weight lost over the next few hours.
- Long or very sweaty sessions (over about an hour) may need electrolytes as well as water.
How to tell if you're drinking enough
- Urine color: pale yellow usually means you're well hydrated. Dark yellow means drink more.
- Thirst: for most healthy people, drinking when thirsty and with meals is enough.
- Signs of dehydration: headache, tiredness, dizziness, dry mouth and urinating less often.
Does coffee count? Can you drink too much?
Yes, coffee, tea, milk and other drinks all count toward your fluids. Caffeine has a mild effect, but regular coffee drinkers still gain most of the water. Water-rich foods like fruit, vegetables and soup count too.
Drinking far more than your kidneys can handle, often several liters in a short time, can dilute the sodium in your blood (hyponatremia). It's rare, but it's a risk during long endurance events, so don't force down water when you aren't thirsty.
See also: how much protein you need and the calorie calculator.
Frequently asked questions
How much water should I drink a day?
A common guide is about 13 cups (3 L) of fluids for men and about 9 cups (2.2 L) for women, with the rest of your water coming from food. You need more in hot weather and when you exercise.
Is 8 glasses of water a day enough?
For many women it's close to the guideline, and food adds more. Men and active people usually need more. Pale yellow urine is a good sign you're drinking enough.
How much water should I drink based on my weight?
A rough rule is half an ounce per pound of body weight, so a 160-pound person would aim for about 80 oz (2.4 L) a day.
Does coffee count as water intake?
Yes. Coffee and tea count toward your daily fluids, even with caffeine.