How much water should you drink a day?
Quick answer: the US National Academies set an adequate daily intake of about 3.7 liters (125 fl oz) of total water for men and 2.7 liters (91 fl oz) for women. About 20% of that usually comes from food, so from drinks that is roughly 13 cups a day for men and 9 cups for women. The popular “8 glasses a day” rule is a reasonable reminder, not a scientific target.
Daily water needs
| Group | Total water (food and drink) | From drinks (about 80%) |
|---|---|---|
| Men 19+ | 3.7 L (125 fl oz) | about 3.0 L (13 cups) |
| Women 19+ | 2.7 L (91 fl oz) | about 2.2 L (9 cups) |
| Pregnancy | 3.0 L | about 2.4 L (10 cups) |
| Breastfeeding | 3.8 L | about 3.1 L (13 cups) |
One US cup is 8 fl oz, or about 237 ml. Our liters to cups converter and fluid ounces to liters converter handle other bottle sizes.
What counts toward your water intake
All drinks count, including milk, tea, coffee and sparkling water. Caffeine has a mild diuretic effect, but regular coffee drinkers still gain net fluid from it. Water-rich foods such as fruit, vegetables, soup and yogurt also count, which is where the 20% from food comes from.
Plain water is still the best everyday choice because it has no calories or added sugar. See how many grams of sugar per day.
When you need more
- Exercise. Drink extra before, during and after, especially for sessions over an hour.
- Hot or humid weather, or high altitude.
- Illness with fever, vomiting or diarrhea.
- Pregnancy and breastfeeding.
How to tell if you are drinking enough
For most healthy people, thirst is a good guide. Pale yellow urine is another easy check. Dark yellow urine, headache, tiredness and dizziness can be signs of dehydration.
Can you drink too much water?
It is rare, but drinking very large amounts in a short time can dilute blood sodium (hyponatremia). This mostly affects endurance athletes who drink far more than they sweat out. People with kidney, heart or liver conditions may be told to limit fluids, so follow medical advice.
Easy ways to drink more water
- Carry a reusable bottle and note how many times you refill it.
- Drink a glass with every meal.
- Add lemon, cucumber or mint for flavor.
- Eat more fruit and vegetables.
Frequently asked questions
How many ounces of water should I drink a day? Roughly 100 fl oz from drinks for men and 72 fl oz for women, more if you are active or it is hot.
Is it OK to drink a gallon of water a day? A gallon is 128 fl oz, which is fine for many active people but more than most need. See how many cups in a gallon.
Does coffee dehydrate you? Not in normal amounts. It counts toward your fluid intake.
This article is general information, not medical advice.