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Performance · Answer

How much water should you drink a day?

US guidelines suggest about 3.7 liters of total water for men and 2.7 for women, including food. Here's what that means and how to tell if you're hydrated.
By Reviewed Updated 1 min read

Quick answer

How much water should you drink a day?

The National Academies set adequate total water intake at about 3.7 liters a day for men and 2.7 liters for women, from all drinks and food. Since food provides roughly 20%, that's about 13 cups of fluids for men and 9 cups for women. Needs rise with heat, exercise and illness. Pale yellow urine is a simple hydration check.

At a glance

Key takeaways

  • Total water guidance: ~3.7 L/day for men and ~2.7 L/day for women.
  • About 20% of water typically comes from food.
  • Needs rise with heat, activity, illness, pregnancy and breastfeeding.
  • Pale yellow urine and rarely feeling thirsty are good signs.

Hydration advice ranges from "8 glasses a day" to carrying a gallon jug everywhere. Here's what the official guidance actually says.

The official recommendations

In 2004, the National Academies of Sciences, Engineering, and Medicine set Adequate Intakes for total water — from all beverages and foods:

  • Men: about 3.7 liters (125 oz) per day
  • Women: about 2.7 liters (91 oz) per day

Because food provides roughly 20% of total water, that works out to about 13 cups of fluids for men and 9 cups for women. These are averages for healthy people in temperate climates, not strict targets.

Why hydration matters

A 2010 review in Nutrition Reviews summarized how water affects physical and cognitive function. Even mild dehydration is associated with impaired mood, concentration and physical performance, and it can contribute to fatigue — see why am I tired all the time. Hydration also affects focus; read what foods help you focus.

When you need more

  • Hot or humid weather
  • Exercise and heavy sweating
  • Illness with fever, vomiting or diarrhea
  • Pregnancy and breastfeeding
  • High altitude

Simple hydration checks

  • Urine color: pale yellow is ideal.
  • Thirst: occasional thirst is normal; constant thirst is a cue.
  • Routine: have a glass with each meal and keep water visible.

What counts

Water is best, but milk, tea, coffee and water-rich foods like fruit, vegetables and soup all contribute. Sugary drinks add calories without much benefit.

Some people, such as those with heart or kidney conditions, may need to limit fluids — follow your clinician's advice. For more energy strategies, see our energy optimization guide.

People also ask

More questions people ask

Does coffee count toward hydration?

Yes. Moderate coffee and tea contribute to daily fluid intake despite caffeine's mild diuretic effect.

Can you drink too much water?

Yes, though it's rare. Drinking very large amounts quickly, especially during long endurance events, can dilute blood sodium.

Is the 8 glasses a day rule true?

It's a rough rule of thumb, not a scientific standard. Many people get enough from a mix of drinks and food.

Answers

More answers

Citations

Sources & references

  1. [1]Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and SulfateNational Academies of Sciences, Engineering, and Medicine · Government resourceView source : Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (opens in a new tab)
  2. [2]Water, hydration, and healthPopkin BM, D'Anci KE, Rosenberg IH. Nutrition Reviews, 2010 · ReviewView source : Water, hydration, and health (opens in a new tab)

Study links open a PubMed search for the exact title, so they keep working even if a journal changes its URL.

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