How much water should you drink a day? The old 8 glasses rule is a rough guide. Your real needs depend on your size, activity and climate. Enter your details for a personalized estimate.
Water Intake Calculator
Estimate for healthy adults: about 35 ml per kg of body weight, plus extra for exercise and heat. Around 20% of your water usually comes from food.
Signs You Need More Water
Dark yellow urine, thirst, headaches, tiredness and dizziness can all be signs you need to drink more. Learn more in our guide to signs you might need more electrolytes.
Easy Ways to Drink More
- Keep a refillable bottle with you.
- Flavor water with citrus, cucumber or mint, or try our lemon lime chia water.
- Eat water-rich foods like watermelon, cucumber, oranges and soups.
Why Hydration Matters
Water makes up about 60% of your body. It regulates temperature, carries nutrients, cushions joints and helps your kidneys clear waste. Even mild dehydration, around 1 to 2% of body weight, can affect your energy, mood and concentration.
General Water Guidelines
The US National Academies suggest a total daily fluid intake of about 2.7 liters (91 oz) for women and 3.7 liters (125 oz) for men from all drinks and food. Needs rise with heat, exercise, illness, pregnancy and breastfeeding. The simplest check: pale yellow urine usually means you’re well hydrated.
Frequently Asked Questions
Does coffee count toward water intake?
Yes. Moderate amounts of coffee and tea still hydrate you overall, despite their mild diuretic effect.
How much water should I drink when exercising?
Add roughly 12 oz (350 ml) for every 30 minutes of exercise, and more in hot weather.
Can you drink too much water?
Yes, though it is rare. Drinking very large amounts quickly can dilute your blood sodium. Spread your intake through the day.
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