At the risk of getting ourselves kicked out of the cool kids club, we're gonna tell you a secret: the "8 x 8 rule" (that's eight 8-ounce glasses of water per day), isn't necessarily a hard and fast law. It's a good guideline, but studies show men actually need closer to 16 cups and women closer to 11, on average. Plus, age, climate, activity level, and illness can all also impact how much water you need.

But wait — before you pick up that gallon-size water bottle, don't think that's the only way to hydrate! Foods with a high water content (like lettuce, tomatoes, and oranges) count toward that H2O goal, as do drinks like tea, coffee, juice, and milk. But despite that big, daunting number, thirst and urine color (yeah, seriously) may actually be better guidelines for when it's time to drink up.

The Takeaway: While studies have given us recommended daily water intakes, there are plenty of ways to get that H2O. Don't get too caught up on a number — thirst is a good guideline.

Watch Out for Toxins

Before chugging out of that plain old water bottle, make sure your water isn't coming with a side of BPA from the plastic it's held in.

Fun Fact:

Over 100 years, a water molecule spends 98 percent of its time in the ocean and only one week in the atmosphere.