According to the Institute of Medicine, women should drink about 91 ounces of water a day and men should consume 125 ounces. But these recommendations aren’t necessarily useful for most people, since they’re based on the idea that we all need different amounts of fluids depending on our size, activity level and climate.

“The thirst mechanism is not very accurate,” says Dr. Alan Goldhamer, founder of TrueNorth Health Center in Santa Rosa, California. “By the time you feel thirsty, you’re already dehydrated.”

So how much should you drink? It depends on your body size and activity level.

The Institute of Medicine recommends that women consume 2.7 liters (about 10 cups) and men 3.8 liters (about 14 cups) each day to maintain health, but there’s not enough research to determine how much water we really need to stay hydrated during exercise or in hot weather — or even what happens if we don’t drink enough during those times.

Last modified: August 3, 2022