How much water should I drink a day?

A reasonable target is about 35 milliliters per kilogram of body weight, plus about 12 ounces for every 30 minutes of exercise, more in heat. For a 170-pound adult that's roughly 90 ounces before exercise.

Is eight glasses a day right?

Eight 8-ounce glasses is 64 ounces, which is on the low side for most adults and doesn't account for size, exercise or climate.

Do coffee and tea count?

Yes. The diuretic effect of caffeine is small at normal intakes, and the fluid still counts toward your total.

What are the official recommendations?

The US National Academies set adequate intake at 2.7 liters a day of total water for women and 3.7 for men. About 20 percent of that comes from food, so the drinking target is lower.

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Water intake calculator

There is no single right amount of water. Body weight, exercise and heat all move the number. This gives a sensible daily target and shows how it compares with the official adequate-intake figures.

Sex

Height

Weight

Exercise a day

minutes

Climate

Water a day

103oz

In cups

12.9 cups

In liters

3 L

Official adequate intake

2.7 L total water

35 ml per kilogram of body weight, plus about 12 oz for every 30 minutes of exercise. The official figure counts all water, including the 20 percent or so that comes from food, which is why it looks higher. Pale yellow urine is the simplest check that you're drinking enough.

Tired even when you're drinking enough?

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Common questions

How much water should I drink a day?: A reasonable target is about 35 milliliters per kilogram of body weight, plus about 12 ounces for every 30 minutes of exercise, more in heat. For a 170-pound adult that's roughly 90 ounces before exercise.
Is eight glasses a day right?: Eight 8-ounce glasses is 64 ounces, which is on the low side for most adults and doesn't account for size, exercise or climate.
Do coffee and tea count?: Yes. The diuretic effect of caffeine is small at normal intakes, and the fluid still counts toward your total.
What are the official recommendations?: The US National Academies set adequate intake at 2.7 liters a day of total water for women and 3.7 for men. About 20 percent of that comes from food, so the drinking target is lower.

More tools

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These calculators give estimates from standard formulas for healthy adults. They are not medical advice and don't account for pregnancy, medical conditions or medications. Decisions about treatment are made by the licensed providers in our network.