Let’s start with the famous “8x8” rule—eight 8-ounce glasses a day. You’ve heard it a million times. Spoiler alert: that’s not a law, it’s a suggestion that might be too low for some, too high for others.
Your actual need depends on your body, your activity level, and—ironically—how much you’re sweating. A marathon runner in July is a different creature than me, typing in an air-conditioned room. You are probably somewhere in between.
The National Academies of Sciences, Engineering, and Medicine gives a range: about 3.7 liters (125 ounces) for men and 2.7 liters (91 ounces) for women per day. But here’s the kicker: that’s total water—from all drinks and food.
