How to use
Enter your weight, how long you exercise each day and whether it’s hot outside. You’ll see roughly how much water to drink a day, in ounces or liters and in cups.
How it’s calculated
- 30 mL per kilogram of body weight (about ½ oz per pound) — the baseline;
- +12 oz (350 mL) for every 30 minutes of exercise — to replace sweat;
- +17 oz (0.5 L) in hot weather.
For example, at 160 lb with 30 minutes of exercise: about 85 oz — roughly 11 cups.
FAQ
Do tea, soup and fruit count? Yes. Your body gets water from all drinks and food — about a fifth comes from food. The result is what to drink, but there’s no need to count every glass.
Do I really need 8 glasses a day? It’s a popular rule of thumb without solid science behind it. The U.S. National Academies suggest about 2.7 L (91 oz) of total water a day for women and 3.7 L (125 oz) for men, including food.
Can you drink too much water? Yes, though it’s rare: several liters in a couple of hours can dangerously lower blood sodium. Spread your drinking through the day and let thirst guide you.
This is a guide for healthy adults. With kidney or heart conditions, or during pregnancy and breastfeeding, ask your doctor how much to drink.